message stringlengths 2 23.8k | message_type stringclasses 2
values | message_id int64 0 1 | conversation_id int64 97 109k | cluster float64 0 0 | __index_level_0__ int64 194 217k |
|---|---|---|---|---|---|
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s of length n consisting of lowercase Latin letters. You may apply some operations to this string: in one operation you can delete some contiguous substring of this string, if all letters in the substring you delete are equal. For example, after deleting substring bbbb from string abbbbaccdd we get the string aaccdd.
Calculate the minimum number of operations to delete the whole string s.
Input
The first line contains one integer n (1 ≤ n ≤ 500) — the length of string s.
The second line contains the string s (|s| = n) consisting of lowercase Latin letters.
Output
Output a single integer — the minimal number of operation to delete string s.
Examples
Input
5
abaca
Output
3
Input
8
abcddcba
Output
4
Submitted Solution:
```
n = int(input())
s = list(input())
from collections import Counter
import itertools
import operator
# abbacaz
def find_separator(texto):
lista = {}
atual = ''
future_list = []
for i in texto:
if i != atual:
future_list.append(i)
atual = i
c = Counter(future_list)
# print(future_list)
# print(c)
return [x for x in range(len(future_list)) if future_list[x]==c.most_common(1)[0][0]], future_list
def custo(texto):
if not texto:
return 0
if len(texto) == 1:
return 1
position, lista = find_separator(texto)
list_sides = lista[0:position[0]]+lista[position[-1]+1:len(lista)]
# print(list_sides)
c = 1
# print(position)
# print('separadores')
for x in range(len(position)-1):
# print(lista[position[x]+1:position[x+1]])
c+=custo(lista[position[x]+1:position[x+1]])
# print(list_sides)
c+=custo(list_sides)
return c
print(custo(s))
# print(s) zbczaabaadcdaeza
# ccacbbbbbbbccbccbccbacbabcaaaabbcbcaabbababcbbcbcbbcbabbacbacbacbcaccccaaccbabcbbbbccbbaacbcbcaaabbbbbaaabbabacacaabcaababcbbcbcababbbabbaaaccbcabcabbbcbcccbcbcacabbbbbacbcbabbcbaabcbcbcacacccabbbccacaacaaccbbabbbaaccabcaaaaacbbcacacbacabbccaaaccccaabbaacbabbcbccababbabacabbcacbcbaaccbcaccabbbbacabcbccbabacbcbaaaacbbcbccacaaaabacaabbaaccabacababcbcbcacbcccccbbabbccbaabcbaaabbcbacacbbbbabbacbabbabbaacccbaababccaaccbaaabcaccaaacbbbcaabcbcbcbccbbbbcbacbccbabcbbcbbbabbcbaccabacbbbabcbcbcbbbacccbabab
``` | instruction | 0 | 66,495 | 0 | 132,990 |
No | output | 1 | 66,495 | 0 | 132,991 |
Evaluate the correctness of the submitted Python 2 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s of length n consisting of lowercase Latin letters. You may apply some operations to this string: in one operation you can delete some contiguous substring of this string, if all letters in the substring you delete are equal. For example, after deleting substring bbbb from string abbbbaccdd we get the string aaccdd.
Calculate the minimum number of operations to delete the whole string s.
Input
The first line contains one integer n (1 ≤ n ≤ 500) — the length of string s.
The second line contains the string s (|s| = n) consisting of lowercase Latin letters.
Output
Output a single integer — the minimal number of operation to delete string s.
Examples
Input
5
abaca
Output
3
Input
8
abcddcba
Output
4
Submitted Solution:
```
from sys import stdin, stdout
from collections import Counter, defaultdict
from itertools import permutations, combinations
raw_input = stdin.readline
pr = stdout.write
mod=10**9+7
def ni():
return int(raw_input())
def li():
return map(int,raw_input().split())
def pn(n):
stdout.write(str(n)+'\n')
def pa(arr):
pr(' '.join(map(str,arr))+'\n')
# fast read function for total integer input
def inp():
# this function returns whole input of
# space/line seperated integers
# Use Ctrl+D to flush stdin.
return map(int,stdin.read().split())
range = xrange # not for python 3.0+
# main code
n=ni()
s=raw_input().strip()
dp=[[0 for i in range(n)] for j in range(n)]
for i in range(1,n):
for j in range(i,n):
dp[j-i][j]=dp[j-i+1][j]+1
for k in range(j-i+1,j+1):
if s[k]==s[j-1]:
dp[j-i][j]=min(dp[j-i][j],dp[j-i+1][k]+dp[k][j])
pn(dp[0][-1]+1)
``` | instruction | 0 | 66,496 | 0 | 132,992 |
No | output | 1 | 66,496 | 0 | 132,993 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Let's introduce the designation <image>, where x is a string, n is a positive integer and operation " + " is the string concatenation operation. For example, [abc, 2] = abcabc.
We'll say that string s can be obtained from string t, if we can remove some characters from string t and obtain string s. For example, strings ab and aсba can be obtained from string xacbac, and strings bx and aaa cannot be obtained from it.
Sereja has two strings, w = [a, b] and q = [c, d]. He wants to find such maximum integer p (p > 0), that [q, p] can be obtained from string w.
Input
The first line contains two integers b, d (1 ≤ b, d ≤ 107). The second line contains string a. The third line contains string c. The given strings are not empty and consist of lowercase English letters. Their lengths do not exceed 100.
Output
In a single line print an integer — the largest number p. If the required value of p doesn't exist, print 0.
Examples
Input
10 3
abab
bab
Output
3 | instruction | 0 | 66,730 | 0 | 133,460 |
Tags: binary search, dfs and similar, strings
Correct Solution:
```
b, p = map(int, input().split())
s1 = input()
s2 = input()
cnt = [0] * len(s2)
nxt = [0] * len(s2)
for i in range(len(s2)):
pos = i
for j in range(len(s1)):
if s1[j] == s2[pos]:
pos += 1
if pos == len(s2):
cnt[i] += 1
pos = 0
nxt[i] = pos
ans = 0
poss = 0
for i in range(b):
ans += cnt[poss]
poss = nxt[poss]
print(ans // p)
``` | output | 1 | 66,730 | 0 | 133,461 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Let's introduce the designation <image>, where x is a string, n is a positive integer and operation " + " is the string concatenation operation. For example, [abc, 2] = abcabc.
We'll say that string s can be obtained from string t, if we can remove some characters from string t and obtain string s. For example, strings ab and aсba can be obtained from string xacbac, and strings bx and aaa cannot be obtained from it.
Sereja has two strings, w = [a, b] and q = [c, d]. He wants to find such maximum integer p (p > 0), that [q, p] can be obtained from string w.
Input
The first line contains two integers b, d (1 ≤ b, d ≤ 107). The second line contains string a. The third line contains string c. The given strings are not empty and consist of lowercase English letters. Their lengths do not exceed 100.
Output
In a single line print an integer — the largest number p. If the required value of p doesn't exist, print 0.
Examples
Input
10 3
abab
bab
Output
3
Submitted Solution:
```
b, p = map(int, input().split())
s1 = input()
s2 = input()
cnt = 0
pos = 0
flag = True
while flag:
for i in range(len(s1)):
if s1[i] == s2[pos]:
pos += 1
if i == len(s1) - 1:
cnt += 1
if pos == len(s2):
flag = False
break
ans = b // cnt // p
print(ans)
``` | instruction | 0 | 66,731 | 0 | 133,462 |
No | output | 1 | 66,731 | 0 | 133,463 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Let's introduce the designation <image>, where x is a string, n is a positive integer and operation " + " is the string concatenation operation. For example, [abc, 2] = abcabc.
We'll say that string s can be obtained from string t, if we can remove some characters from string t and obtain string s. For example, strings ab and aсba can be obtained from string xacbac, and strings bx and aaa cannot be obtained from it.
Sereja has two strings, w = [a, b] and q = [c, d]. He wants to find such maximum integer p (p > 0), that [q, p] can be obtained from string w.
Input
The first line contains two integers b, d (1 ≤ b, d ≤ 107). The second line contains string a. The third line contains string c. The given strings are not empty and consist of lowercase English letters. Their lengths do not exceed 100.
Output
In a single line print an integer — the largest number p. If the required value of p doesn't exist, print 0.
Examples
Input
10 3
abab
bab
Output
3
Submitted Solution:
```
b, p = map(int, input().split())
s1 = input()
s2 = input()
cnt = 0
pos = 0
flag = True
while flag and cnt < b:
for i in range(len(s1)):
if i == 0:
cnt += 1
if s1[i] == s2[pos]:
pos += 1
if pos == len(s2):
flag = False
break
if flag == False:
ans = b // cnt // p
else:
ans = 0
print(ans)
``` | instruction | 0 | 66,732 | 0 | 133,464 |
No | output | 1 | 66,732 | 0 | 133,465 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Let's introduce the designation <image>, where x is a string, n is a positive integer and operation " + " is the string concatenation operation. For example, [abc, 2] = abcabc.
We'll say that string s can be obtained from string t, if we can remove some characters from string t and obtain string s. For example, strings ab and aсba can be obtained from string xacbac, and strings bx and aaa cannot be obtained from it.
Sereja has two strings, w = [a, b] and q = [c, d]. He wants to find such maximum integer p (p > 0), that [q, p] can be obtained from string w.
Input
The first line contains two integers b, d (1 ≤ b, d ≤ 107). The second line contains string a. The third line contains string c. The given strings are not empty and consist of lowercase English letters. Their lengths do not exceed 100.
Output
In a single line print an integer — the largest number p. If the required value of p doesn't exist, print 0.
Examples
Input
10 3
abab
bab
Output
3
Submitted Solution:
```
b, p = map(int, input().split())
s1 = input()
s2 = input()
cnt = 0
pos = 0
flag = True
while flag and cnt < b:
for i in range(len(s1)):
if i == 0:
cnt += 1
if s1[i] == s2[pos]:
pos += 1
if pos == len(s2):
flag = False
break
if flag:
ans = b // cnt // p
else:
ans = 0
print(ans)
``` | instruction | 0 | 66,733 | 0 | 133,466 |
No | output | 1 | 66,733 | 0 | 133,467 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Vasily the Bear loves beautiful strings. String s is beautiful if it meets the following criteria:
1. String s only consists of characters 0 and 1, at that character 0 must occur in string s exactly n times, and character 1 must occur exactly m times.
2. We can obtain character g from string s with some (possibly, zero) number of modifications. The character g equals either zero or one.
A modification of string with length at least two is the following operation: we replace two last characters from the string by exactly one other character. This character equals one if it replaces two zeros, otherwise it equals zero. For example, one modification transforms string "01010" into string "0100", two modifications transform it to "011". It is forbidden to modify a string with length less than two.
Help the Bear, count the number of beautiful strings. As the number of beautiful strings can be rather large, print the remainder after dividing the number by 1000000007 (109 + 7).
Input
The first line of the input contains three space-separated integers n, m, g (0 ≤ n, m ≤ 105, n + m ≥ 1, 0 ≤ g ≤ 1).
Output
Print a single integer — the answer to the problem modulo 1000000007 (109 + 7).
Examples
Input
1 1 0
Output
2
Input
2 2 0
Output
4
Input
1 1 1
Output
0
Note
In the first sample the beautiful strings are: "01", "10".
In the second sample the beautiful strings are: "0011", "1001", "1010", "1100".
In the third sample there are no beautiful strings.
Submitted Solution:
```
MOD = 10**9 + 7
n,m,g = map (int,input().split())
fact = [1,1]
for i in range (2,m+n+1):
fact.append (i*fact[len(fact)-1]%MOD)
def C (n,k):
return fact[n] // fact[k] // fact[n-k]
ret = 0
if m == 0:
if n % 2 == 0 and g == 1:
ret += 1
elif n % 2 == 1 and g == 0:
ret += 1
else:
if m == 1:
if n % 2 == 0:
if g == 1: ret += 1
else: ret -= 1
else:
if g == 1: ret -= 1
else: ret += 1
R = range (0 if g==0 else 1, n+1, 2)
for i in R:
ret = (ret + C(m+n-i-1,n-i)) % MOD
print (ret)
``` | instruction | 0 | 66,734 | 0 | 133,468 |
No | output | 1 | 66,734 | 0 | 133,469 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Vasily the Bear loves beautiful strings. String s is beautiful if it meets the following criteria:
1. String s only consists of characters 0 and 1, at that character 0 must occur in string s exactly n times, and character 1 must occur exactly m times.
2. We can obtain character g from string s with some (possibly, zero) number of modifications. The character g equals either zero or one.
A modification of string with length at least two is the following operation: we replace two last characters from the string by exactly one other character. This character equals one if it replaces two zeros, otherwise it equals zero. For example, one modification transforms string "01010" into string "0100", two modifications transform it to "011". It is forbidden to modify a string with length less than two.
Help the Bear, count the number of beautiful strings. As the number of beautiful strings can be rather large, print the remainder after dividing the number by 1000000007 (109 + 7).
Input
The first line of the input contains three space-separated integers n, m, g (0 ≤ n, m ≤ 105, n + m ≥ 1, 0 ≤ g ≤ 1).
Output
Print a single integer — the answer to the problem modulo 1000000007 (109 + 7).
Examples
Input
1 1 0
Output
2
Input
2 2 0
Output
4
Input
1 1 1
Output
0
Note
In the first sample the beautiful strings are: "01", "10".
In the second sample the beautiful strings are: "0011", "1001", "1010", "1100".
In the third sample there are no beautiful strings.
Submitted Solution:
```
MOD = 10**9 + 7
n,m,g = map (int,input().split())
fact = [1,1]
for i in range (2,m+n+1):
fact.append (i*fact[len(fact)-1]%MOD)
def C (n,k):
return fact[n] // fact[k] // fact[n-k]
ret = 0
if m == 1:
if n % 2 == 0:
if g == 1: ret += 1
else: ret -= 1
else:
if g == 1: ret -= 1
else: ret += 1
R = range (0 if g==0 else 1, n+1, 2)
for i in R:
ret = (ret + C(m+n-i-1,n-i)) % MOD
print (ret)
``` | instruction | 0 | 66,735 | 0 | 133,470 |
No | output | 1 | 66,735 | 0 | 133,471 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,969 | 0 | 133,938 |
Tags: greedy, strings
Correct Solution:
```
s = list(input())
word = 'a'
for i in range(len(s)):
if s[i] <= word:
s[i] = word
word = chr(ord(word) + 1)
if word > 'z':
break
if word <= 'z':
print(-1)
else:
print(''.join(s))
``` | output | 1 | 66,969 | 0 | 133,939 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,970 | 0 | 133,940 |
Tags: greedy, strings
Correct Solution:
```
def next_char(c):
return chr(ord(c) + 1)
s = list(input().strip())
c = 'a'
for i in range(len(s)):
if s[i] <= c:
s[i] = c
c = next_char(c)
if ord(c) > ord('z'):
break
if ord(c) <= ord('z'):
print(-1)
else:
print(*s, sep='')
``` | output | 1 | 66,970 | 0 | 133,941 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,971 | 0 | 133,942 |
Tags: greedy, strings
Correct Solution:
```
s = input()
l = list(s)
t = 'abcdefghijklmnopqrstuvwxyz'
i = 0
n = len(l)
impossible = False
for c in t:
for j in range(i, n):
if l[j] <= c:
l[j] = c
i = j + 1
break
else:
impossible = True
if impossible:
print(-1)
else:
print(''.join(l))
``` | output | 1 | 66,971 | 0 | 133,943 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,972 | 0 | 133,944 |
Tags: greedy, strings
Correct Solution:
```
def solve(stg):
check = False
stg = list(stg)
x = 'a'
for i in range(len(stg)):
if stg[i] <= x:
stg[i] = x
x = chr(ord(x) + 1)
if x > 'z':
check = True
break
if check:
stg = ''.join(stg)
return stg
return -1
def string_transformation(stg):
return solve(stg)
if __name__ == "__main__":
stg = input()
print(string_transformation(stg))
``` | output | 1 | 66,972 | 0 | 133,945 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,973 | 0 | 133,946 |
Tags: greedy, strings
Correct Solution:
```
x = "abcdefghijklmnopqrstuvwxyz"
y = str(input())
yLista =list(y)
k=0
t=0
if(len(x)>len(y)):
k=1
else:
for i in range(len(y)):
if(t>=26):
continue
if(x[t]==yLista[i]):
t = t+1
continue
if(x[t]>=yLista[i]):
yLista[i]=x[t]
t=t+1
pos = 0
for i in range(len(y)):
if(yLista[i]==x[pos]):
pos = pos+1
if(pos==26):
break
if(pos!=26):
k=1
y = ''.join (yLista)
if(k==0 and t==len(x)):
print(y)
else:
print(-1)
``` | output | 1 | 66,973 | 0 | 133,947 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,974 | 0 | 133,948 |
Tags: greedy, strings
Correct Solution:
```
'''
Auther: ghoshashis545 Ashis Ghosh
College: Jalpaiguri Govt Enggineering College
'''
from os import path
from io import BytesIO, IOBase
import sys
from heapq import heappush,heappop
from functools import cmp_to_key as ctk
from collections import deque,Counter,defaultdict as dd
from bisect import bisect,bisect_left,bisect_right,insort,insort_left,insort_right
from itertools import permutations
from datetime import datetime
from math import ceil,sqrt,log,gcd
def ii():return int(input())
def si():return input().rstrip()
def mi():return map(int,input().split())
def li():return list(mi())
abc='abcdefghijklmnopqrstuvwxyz'
mod=1000000007
#mod=998244353
inf = float("inf")
vow=['a','e','i','o','u']
dx,dy=[-1,1,0,0],[0,0,1,-1]
def bo(i):
return ord(i)-ord('a')
file = 1
def ceil(a,b):
return (a+b-1)//b
def solve():
# for _ in range(1,ii()+1):
s = list(si())
c = 0
for i in range(len(s)):
if bo(s[i])==c:
c+=1
elif bo(s[i]) <= c:
s[i] = chr(97 + c)
c+=1
if c==26:
break
if c==26:
print("".join(s))
else:
print(-1)
if __name__ =="__main__":
if(file):
if path.exists('input.txt'):
sys.stdin=open('input.txt', 'r')
sys.stdout=open('output.txt','w')
else:
input=sys.stdin.readline
solve()
``` | output | 1 | 66,974 | 0 | 133,949 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,975 | 0 | 133,950 |
Tags: greedy, strings
Correct Solution:
```
str = input("")
str_len = len(str)
cur = 'a'
res = ""
for i in range(0,str_len):
if str[i] <= cur <= 'z':
res += cur
cur = chr(ord(cur)+1)
else:
res += str[i]
if ord(cur)!= ord('z')+1:
print("-1")
else:
print(res)
``` | output | 1 | 66,975 | 0 | 133,951 |
Provide tags and a correct Python 3 solution for this coding contest problem.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1 | instruction | 0 | 66,976 | 0 | 133,952 |
Tags: greedy, strings
Correct Solution:
```
s = list(input())
st = 'a'
for i in range(len(s)):
if (s[i] <= st):
s[i] = st
st = chr(ord(st) + 1)
if st > 'z':
break
if (st <= 'z'):
print(-1)
else:
print(*s,sep = '')
``` | output | 1 | 66,976 | 0 | 133,953 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
alf = list(input())
n = len(alf)
if n < 26:
print(-1)
else:
alphabet = "abcdefghijklmnopqrstuvwxyz"
m = 0
for i in range(n):
#print(m, i, alphabet[m], alf[i])
if alf[i] <= alphabet[m]:
alf[i] = alphabet[m]
m+=1
if m == 26:
print("".join(alf))
break
elif n-(i+1)<26-(m+1):
break
if m < 26:
print(-1)
``` | instruction | 0 | 66,977 | 0 | 133,954 |
Yes | output | 1 | 66,977 | 0 | 133,955 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
sequence = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p',
'q','r','s','t','u','v','w','x','y','z']
st = list(input())
ind = 0
for i in range(len(st)):
if(st[i]<=sequence[ind]):
st[i] = sequence[ind]
ind+=1
if(ind == 26):
break
if ind == 26:
print("".join(st))
else:
print(-1)
``` | instruction | 0 | 66,978 | 0 | 133,956 |
Yes | output | 1 | 66,978 | 0 | 133,957 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
s = input()
def aln(c):
return ord(c) - ord('A') -31
def nal(n):
return chr(n+96)
a = []
for i in range(len(s)):
a.append(aln(s[i]))
tar = 1
for i in range(len(s)):
if a[i] != tar and a[i] < tar:
a[i] = tar
tar = tar + 1
if a[i] == tar:
tar = tar + 1
if tar == 27:
break
if tar == 27:
ans = ''
for i in range(len(s)):
ans += nal(a[i])
print(ans)
else:
print(-1)
``` | instruction | 0 | 66,979 | 0 | 133,958 |
Yes | output | 1 | 66,979 | 0 | 133,959 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
s=input()
p=''
k='abcdefghijklmnopqrstuvwxyzz'
check=False
i=0
for c in s:
p=(p+k[i]) if c<=k[i] and i<26 else p+c
i=i+1 if c<=k[i] and i<26 else i
check=True if i==26 else False
print(p if check else -1)
``` | instruction | 0 | 66,980 | 0 | 133,960 |
Yes | output | 1 | 66,980 | 0 | 133,961 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
sequence = ['a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p',
'q','r','s','t','u','v','w','x','y','z']
st = list(input())
worked = True
for i in range(len(st)):
if(st[i]<=sequence[i%26]):
st[i] = sequence[i%26]
else:
worked = False
if worked:
print("".join(st))
else:
print(-1)
``` | instruction | 0 | 66,981 | 0 | 133,962 |
No | output | 1 | 66,981 | 0 | 133,963 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
'''input
thereisnoanswer
'''
def check(a, b):
if ord(a) <= ord(b):
return 1
return 0
def find(a):
n = len(a)
if n < 26:
return -1
r = list("abcdefghijklmnopqrstuvwxyz")
j = 0
cur = r[j]
for i in range(n):
if check(a[i], cur):
a[i] = cur
j += 1
if j == 26:
break
cur = r[j]
return ''.join(a)
a = list(input())
ans = find(a)
print(ans)
``` | instruction | 0 | 66,982 | 0 | 133,964 |
No | output | 1 | 66,982 | 0 | 133,965 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
a=input()
b=len(a)
c=0
final=[]
if b>26:
print('-1')
else:
for i in range(len(a)):
if ord(a[i])>ord('z')-b+1+i:
print('-1')
c=1
break
if c==0:
for j in range(len(a)):
final.append(chr(ord('z')-b+1+j))
print(''.join(final))
``` | instruction | 0 | 66,983 | 0 | 133,966 |
No | output | 1 | 66,983 | 0 | 133,967 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
You are given a string s consisting of |s| small english letters.
In one move you can replace any character of this string to the next character in alphabetical order (a will be replaced with b, s will be replaced with t, etc.). You cannot replace letter z with any other letter.
Your target is to make some number of moves (not necessary minimal) to get string abcdefghijklmnopqrstuvwxyz (english alphabet) as a subsequence. Subsequence of the string is the string that is obtained by deleting characters at some positions. You need to print the string that will be obtained from the given string and will be contain english alphabet as a subsequence or say that it is impossible.
Input
The only one line of the input consisting of the string s consisting of |s| (1 ≤ |s| ≤ 105) small english letters.
Output
If you can get a string that can be obtained from the given string and will contain english alphabet as a subsequence, print it. Otherwise print «-1» (without quotes).
Examples
Input
aacceeggiikkmmooqqssuuwwyy
Output
abcdefghijklmnopqrstuvwxyz
Input
thereisnoanswer
Output
-1
Submitted Solution:
```
s = input()
length = len(s)
if length < 26:
print('-1')
S = list(s)
pos = 0
current = ord('a')
while pos < length and current <= ord('z'):
val = ord(S[pos])
if val == current:
current += 1
elif val < current:
S[pos] = chr(current)
current += 1
pos += 1
if current > ord('z'):
print(''.join(S))
else:
print('-1')
``` | instruction | 0 | 66,984 | 0 | 133,968 |
No | output | 1 | 66,984 | 0 | 133,969 |
Provide a correct Python 3 solution for this coding contest problem.
The unlucky Ikta-kun has rewritten the important character string T that he had to a different character string T'by the virus. It is known that the virus has rewritten one letter of T to a different letter. That is, T and T'are different by exactly one character. In order to restore T, Ikta prepared a document S in which T appears. As a preparation for restoring T, I would like to find out the number of substrings of S that may match T.
Given the string T'and the document S. S = a1 a2 a3 .. .a | S | length | T'| substring ak ak + 1 ... ak + | T'| −1 (1 ≤ k ≤ | S | − | T'| Find the number of things that differ by one character from T'in +1).
Input
The input is given in the following format.
S
T'
* S is given in the first line.
* T'is given in the second line.
* S and T'consist only of uppercase and lowercase alphabets, respectively.
Constraints
Each variable being input satisfies the following constraints.
* 1 ≤ | S | ≤ 300,000
* 1 ≤ | T'| ≤ | S |
Output
Output the number of substrings that satisfy the conditions on one line.
Examples
Input
abcbcdbc
abc
Output
2
Input
aaaaaa
aaaaaa
Output
0
Input
baaaaaaaa
b
Output
8 | instruction | 0 | 67,215 | 0 | 134,430 |
"Correct Solution:
```
import string
import sys
readline = sys.stdin.readline
write = sys.stdout.write
def solve():
s0 = "^" + string.ascii_uppercase + string.ascii_lowercase
*S, = map(s0.index, readline().strip()); N = len(S)
*T, = map(s0.index, readline().strip()); M = len(T)
base = 59; mod = 10**9 + 9
pw = [1]*(N+1)
r = 1
for i in range(N):
pw[i+1] = r = r * base % mod
h0 = [0]*(M+1)
r = 0
for i in range(M):
h0[i+1] = r = (r * base + T[i]) % mod
h1 = [0]*(N+1)
r = 0
for i in range(N):
h1[i+1] = r = (r * base + S[i]) % mod
ans = 0
for i in range(N-M+1):
left = 0; right = M+1
while left+1 < right:
mid = (left + right) >> 1
if h0[mid] == (h1[mid+i] - h1[i] * pw[mid]) % mod:
left = mid
else:
right = mid
if left < M:
if (h0[M] - h0[left+1] * pw[M - (left+1)]) % mod == (h1[M+i] - h1[i+left+1] * pw[M - (left+1)]) % mod:
ans += 1
write("%d\n" % ans)
solve()
``` | output | 1 | 67,215 | 0 | 134,431 |
Provide a correct Python 3 solution for this coding contest problem.
Problem
Here is a list of strings. Let's take a break and play with shiritori. Shiritori is performed according to the following rules.
1. First of all, select one of your favorite strings from the list and exclude that string from the list.
2. Next, select one character string from the list in which the last character of the previously selected character string is the first character.
3. Exclude the selected string from the list.
After this, steps 2 and 3 will be repeated alternately.
Now, let's assume that this shiritori is continued until there are no more strings to select from the list in 2. At this time, I want to list all the characters that can be the "last character" of the last selected character string.
Constraints
The input satisfies the following conditions.
* $ 1 \ le N \ lt 10 ^ 4 $
* $ 1 \ le | s_i | \ lt 100 $
* $ s_i \ neq s_j (i \ neq j) $
* The string contains only lowercase letters
Input
$ N $
$ s_1 $
$ s_2 $
$ s_3 $
::
$ s_N $
The number of strings $ N $ is given on the first line.
The following $ N $ line is given a list of strings.
Output
Output the characters that can be the "last character" of the last selected character string in ascending order from a to z in lexicographical order.
Examples
Input
5
you
ate
my
hum
toast
Output
e
t
u
Input
7
she
sells
sea
shells
by
the
seashore
Output
a
e
y | instruction | 0 | 67,218 | 0 | 134,436 |
"Correct Solution:
```
import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians
from itertools import accumulate, permutations, combinations, product, groupby, combinations_with_replacement
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = 10**10
mod = 10 ** 9 + 7
class Dinic:
def __init__(self, v, inf=10**10):
self.v = v
self.inf = inf
self.G = [[] for _ in range(v)]
self.level = [-1]*v # 深さ
self.ite = [0]*v # DFSでの探索が済んでいるか
def add_edge(self, fr, to, cap):
self.G[fr].append([to, cap, len(self.G[to])])
self.G[to].append([fr, 0, len(self.G[fr])-1])
def bfs(self, s): # BFSで深さ決定,sがstart
self.level = [-1]*self.v # 必要
self.level[s] = 0
Q = deque()
Q.append(s)
while Q:
v = Q.popleft()
for i in range(len(self.G[v])):
e = self.G[v][i]
if e[1]>0 and self.level[e[0]]<0: ###capacity>0かつtoの深さ未定
self.level[e[0]] = self.level[v]+1
Q.append(e[0])
def dfs(self, v, t, f): # DFSで増加パス探索,v開始、t終点、総フローf
if v==t:
return f
for i in range(self.ite[v], len(self.G[v])):
self.ite[v] = i
e = self.G[v][i]
if e[1]>0 and self.level[v]<self.level[e[0]]:
d = self.dfs(e[0], t, min(f, e[1]))
if d>0:
e[1] -= d # cap減少
self.G[e[0]][e[2]][1] += d # 逆辺のcap増加
return d
return 0
def max_flow(self, s, t):
flow = 0
while True:
self.bfs(s)
if self.level[t]<0:
return flow
self.ite = [0]*self.v # DFSでの探索が済んでいるか否か
f = self.dfs(s,t,self.inf)
while f>0:
flow += f
f = self.dfs(s,t,self.inf)
def ctoi(c):
return ord(c) - ord('a')
N = INT()
S = [input() for _ in range(N)]
ans = []
for i in range(len(ascii_lowercase)):
D = Dinic(len(ascii_lowercase)+2)
s = 26
t = s+1
deg_in = 0
deg_out = 0
for x in S:
u = ctoi(x[0])
v = ctoi(x[-1])
if u == i:
u = s
deg_out += 1
if v == i:
v = t
deg_in += 1
D.add_edge(u, v, 1)
f = D.max_flow(s, t)
if f >= deg_out and deg_in > 0:
ans.append(ascii_lowercase[i])
print(*ans, sep="\n")
``` | output | 1 | 67,218 | 0 | 134,437 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,323 | 0 | 134,646 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
s = str(input())
lst = []
l = 0
h = len(s)-1
while(h>=l):
if s[l] == s[h]:
lst.append(s[l])
l = l+1
h = h-1
elif s[l] == s[h-1]:
h = h-1
elif s[l+1] == s[h]:
l = l+1
else:
l = l+1
h = h-1
lst1 = lst[::-1]
for i in range(len(lst)):
print(lst[i],end = '')
for i in range(1,len(lst)):
print(lst1[i],end = '')
print()
``` | output | 1 | 67,323 | 0 | 134,647 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,324 | 0 | 134,648 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
s=input()
char=set()
n=len(s)
i=0
j=n-1
fin=''
lis=[]
while(j>=i+3):
if s[i]==s[j]:
lis.append(i)
i+=1
j-=1
elif s[i]==s[j-1]:
lis.append(i)
i+=1
j-=2
elif s[i+1]==s[j]:
lis.append(i+1)
i+=2
j-=1
else:
lis.append(i+1)
i+=2
j-=2
fin=''.join([s[k] for k in lis])
fin_rev=fin[::-1]
if j>=i:
fin+=s[i]
print(fin+fin_rev)
``` | output | 1 | 67,324 | 0 | 134,649 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,325 | 0 | 134,650 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
s = input()
if len(s) == 3:
print(s[0])
else:
ans = ["a"] * (len(s) // 4)
for i in range(len(s) // 4):
#print(s[2*i + 1], s[-2*i - 1], s[2*i], s[-2*i - 2])
#print(2*i + 1, -2*i - 1, 2*i, -2*i - 2)
if s[2*i + 1] == s[-2*i - 1]:
ans[i] = s[2*i + 1]
elif s[2*i + 1] == s[-2*i - 2]:
ans[i] = s[2*i + 1]
elif s[2*i] == s[-2*i - 1]:
ans[i] = s[2*i]
elif s[2*i] == s[-2*i - 2]:
ans[i] = s[2*i]
else:
print("What???????")
if len(s) % 4 != 0:
ans = "".join(ans) + s[len(s) // 2] + "".join(ans[::-1])
else:
ans = "".join(ans) + "".join(ans[::-1])
print(ans)
``` | output | 1 | 67,325 | 0 | 134,651 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,326 | 0 | 134,652 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
s = input()
p = 0
k = len(s) - 1
dl = 0
odp = []
while p + 1 < k - 1:
if s[p] == s[k]:
odp.append(s[p])
p += 1
k -= 1
dl += 2
elif s[p] == s[k-1]:
odp.append(s[p])
p += 1
k -= 2
elif s[p+1] == s[k]:
odp.append(s[p+1])
p += 2
k -= 1
else:
odp.append(s[p+1])
p += 2
k -= 2
srodek = 0
if k - p == 2:
x = [s[p], s[p+1], s[p+2]]
x.sort()
if x[0] == x[1]:
odp.append(x[0])
elif x[1] == x[2]:
odp.append(x[1])
else:
srodek = x[1]
if k - p == 1:
if s[p] == s[p+1]:
odp.append(s[p])
else:
srodek = s[p]
if k == p:
srodek = s[p]
if srodek == 0:
if len(odp) * 2 >= len(s)//2:
for i in odp:
print(i, end = "")
for i in range(len(odp)):
j = len(odp) - 1 - i
print(odp[j], end = "")
else:
print("IMPOSSIBLE")
else:
if (2*len(odp) + 1) >= len(s)//2:
for i in odp:
print(i, end = "")
print(srodek, end = "")
for i in range(len(odp)):
j = len(odp) - 1 - i
print(odp[j], end = "")
else:
print("IMPOSSIBLE")
``` | output | 1 | 67,326 | 0 | 134,653 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,327 | 0 | 134,654 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
from collections import deque
s = input()
left = deque([])
right = deque([])
def solve():
l,r = 0, len(s)
while(l<=r):
if(r-l == 0):
print("".join(left+right))
return
elif(r-l <= 3):
print("".join(left+deque([s[l]])+right))
return
if('a' in s[l:l+2] and 'a' in s[r-2:r]):
left.append('a')
right.appendleft('a')
elif('b' in s[l:l+2] and 'b' in s[r-2:r]):
left.append('b')
right.appendleft('b')
else:
left.append('c')
right.appendleft('c')
l+=2
r-=2
solve()
``` | output | 1 | 67,327 | 0 | 134,655 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,328 | 0 | 134,656 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
s=input()
length=len(s)
left=0
right=len(s)-1
endStr=""
while left<right-2:
if s[left]==s[right]:
endStr=endStr+s[left]
left+=1
right-=1
elif s[left]==s[right-1]:
endStr=endStr+s[left]
left+=1
right-=2
elif s[left+1]==s[right]:
endStr=endStr+s[right]
left+=2
right-=1
else:
endStr=endStr+s[left+1]
left+=2
right-=2
endStr=endStr+s[left]+endStr[::-1]
if len(s)//2>len(endStr):
print("IMPOSSIBLE")
else:
print(endStr)
``` | output | 1 | 67,328 | 0 | 134,657 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,329 | 0 | 134,658 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
from sys import stdin, stdout
#N = int(input())
s = input()
N = len(s)
#W,H = [int(x) for x in stdin.readline().split()]
#arr = [int(x) for x in stdin.readline().split()]
required = N//2
front = []
tail = []
left = 0
right = N-1
while left<=right and required>0:
A = left
B = left+1
C = right-1
D = right
if required==1:
front.append(s[A])
required -= 1
break
if s[A]==s[D]:
front.append(s[A])
tail.append(s[A])
left = A+1
right = D-1
elif s[A]==s[C]:
front.append(s[A])
tail.append(s[A])
left = A+1
right = C-1
elif s[B]==s[D]:
front.append(s[B])
tail.append(s[B])
left = B+1
right = D-1
elif s[B]==s[C]:
front.append(s[B])
tail.append(s[B])
left = B+1
right = C-1
required -= 2
#print(left,right,front)
if required==0:
tail = tail[::-1]
print(*front,*tail,sep='')
else:
print('IMPOSSIBLE')
``` | output | 1 | 67,329 | 0 | 134,659 |
Provide tags and a correct Python 3 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,330 | 0 | 134,660 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
import sys
for line in sys.stdin:
line = line[:-1]
ans = ['a']*(len(line)//4)
for i in range(len(line)//4):
if line[2*i] in {line[-2*i-1], line[-2*i-2]}:
ans[i] = line[2*i]
else:
ans[i] = line[2*i+1]
if len(line)%2 ==1 or len(line)%4 == 2:
print("".join(ans) + line[len(line)//2] + "".join(ans[::-1]))
else:
print("".join(ans) + "".join(ans[::-1]))
break
``` | output | 1 | 67,330 | 0 | 134,661 |
Provide tags and a correct Python 2 solution for this coding contest problem.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc". | instruction | 0 | 67,331 | 0 | 134,662 |
Tags: brute force, constructive algorithms, greedy, strings
Correct Solution:
```
from sys import stdin, stdout
from collections import Counter, defaultdict
from itertools import permutations, combinations
raw_input = stdin.readline
pr = stdout.write
def in_num():
return int(raw_input())
def in_arr():
return map(int,raw_input().split())
def pr_num(n):
stdout.write(str(n)+'\n')
def pr_arr(arr):
pr(' '.join(map(str,arr))+'\n')
# fast read function for total integer input
def inp():
# this function returns whole input of
# space/line seperated integers
# Use Ctrl+D to flush stdin.
return map(int,stdin.read().split())
range = xrange # not for python 3.0+
# main code
r=raw_input().strip()
n=len(r)
l1=0
r1=n-1
ans=[]
while r1-l1>=3:
#print l1,r1,ans,
if r[l1]==r[r1]:
#print 1
ans.append(r[l1])
l1+=1
r1-=1
elif r[l1]==r[r1-1]:
#print 2
ans.append(r[l1])
l1+=1
r1-=2
elif r[l1+1]==r[r1]:
#print 3
ans.append(r[l1+1])
l1+=2
r1-=1
else:
#print 4
ans.append(r[l1+1])
l1+=2
r1-=2
#print ans
if r1>=l1:
ans.append(r[l1])
ans=''.join(ans)
pr(ans+''.join(reversed(ans[:-1])))
exit()
ans=''.join(ans)
pr(ans+''.join(reversed(ans)))
``` | output | 1 | 67,331 | 0 | 134,663 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
sre = input()
pre = 0
kre = len(sre) - 1
pointeree = 0
plotttt = []
while (pre + 1 < kre - 1):
if( sre[ pre ] == sre[ kre ]):
plotttt.append( sre[ pre ])
pre += 1
kre -= 1
pointeree += 2
elif (sre[ pre ] == sre[ kre - 1]):
plotttt.append( sre[ pre ])
pre += 1
kre -= 2
elif( sre[ pre + 1] == sre[ kre ]):
plotttt.append( sre[ pre + 1 ])
pre += 2
kre -= 1
else:
plotttt.append( sre[ pre + 1 ])
pre += 2
kre -= 2
dfdkngkfgjfb = 0
if (kre - pre == 2):
xrere = [ sre[ pre ], sre[ pre + 1], sre[ pre + 2 ]]
xrere.sort()
if( xrere[0] == xrere[1]):
plotttt.append( xrere[ 0 ])
elif (xrere[ 1 ] == xrere[ 2 ]):
plotttt.append( xrere[ 1 ])
else:
dfdkngkfgjfb = xrere[ 1 ]
if( kre - pre == 1):
if( sre[ pre] == sre[ pre + 1 ]):
plotttt.append( sre[ pre ])
else:
dfdkngkfgjfb = sre[ pre ]
if (kre == pre):
dfdkngkfgjfb = sre[ pre ]
if( dfdkngkfgjfb == 0):
if ( len( plotttt) * 2 >= len( sre )//2):
for i in plotttt:
print(i, end = "")
for i in range(len(plotttt)):
j = len( plotttt ) - 1 - i
print(plotttt[j], end = "")
else:
print("IMPOSSIBLE")
else:
if ( 2 * len( plotttt ) + 1) >= len( sre )//2:
for i in plotttt:
print(i, end = "")
print( dfdkngkfgjfb, end = "")
for i in range(len( plotttt )):
j = len( plotttt ) - 1 - i
print( plotttt[ j ], end = "")
else:
print("IMPOSSIBLE")
``` | instruction | 0 | 67,332 | 0 | 134,664 |
Yes | output | 1 | 67,332 | 0 | 134,665 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s = input()
n = len(s)
# x = 0
# y = n-1
# ans = ''
# flag = False
#
# while x < y - 2:
# if s[x] == s[y] or s[x] == s[y-1]:
# ans += s[x]
# else:
# ans += s[x+1]
# x += 2
# y -= 2
#
# if y - x >= 1:
# print(ans + s[x] + ans[::-1])
# else:
# print(ans + ans[::-1])
i, j = 0, n - 1
ans = []
t = n // 4
for i in range(t):
x = i*2
y = n - 2 - i * 2
if s[x] == s[y] or s[x] == s[y+1]:
ans.append(s[x])
else:
ans.append(s[x+1])
if n % 4 >= 2:
ans = ans + [s[n // 2]] + ans[::-1]
else:
ans = ans+ans[::-1]
print(''.join(ans))
``` | instruction | 0 | 67,333 | 0 | 134,666 |
Yes | output | 1 | 67,333 | 0 | 134,667 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s=list(input().rstrip())
n=len(s)
i=0
j=n-1
d=[]
while j-i>1:
#print(i,j,s[i],s[j],s[j-1])
if s[i]==s[j]:
d.append(s[i])
i+=1
j-=1
elif s[i]==s[j-1]:
d.append(s[i])
j-=2
i+=1
else:
i+=1
#print(d)
if i<=j:
d.append(s[i])
d+=d[:len(d)-1][::-1]
else:
d+=d[::-1]
print("".join(d))
``` | instruction | 0 | 67,334 | 0 | 134,668 |
Yes | output | 1 | 67,334 | 0 | 134,669 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
from sys import stdin, stdout, exit
s = stdin.readline().strip()
n = len(s)
ans_head = []
ans_tail = []
idx_h = 0
idx_t = n-1
while idx_h+1 < idx_t-1:
heads = set([s[idx_h], s[idx_h+1]])
if s[idx_t] in heads:
ans_head.append(s[idx_t])
ans_tail.append(s[idx_t])
else:
ans_head.append(s[idx_t-1])
ans_tail.append(s[idx_t-1])
idx_h += 2
idx_t -= 2
if n % 4 != 0:
ans_head.append(s[(n+1)//2])
ans = ''.join(ans_head) + ''.join(reversed(ans_tail))
stdout.write(ans + "\n")
``` | instruction | 0 | 67,335 | 0 | 134,670 |
Yes | output | 1 | 67,335 | 0 | 134,671 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s=input()
ss=s[::-1]
n=len(s)
DP=[[0]*(n+1) for _ in range(n+1)]
for i in range(n):
for j in range(n):
if s[i]==ss[j]:
DP[i+1][j+1]=DP[i][j]+1
else:
DP[i+1][j+1]=max(DP[i+1][j],DP[i][j+1])
if DP[n][n]<n//2:
"IMPOSSIBLE"
else:
Ans=""
l=0
for i in reversed(range(n)):
if DP[n][i]<DP[n][i+1]:
Ans+=ss[i]
l+=1
if l==n//2:
break
if l<n//2:
for i in reversed(range(n)):
if DP[i][0]<DP[i+1][0]:
Ans+=s[i]
l+=1
if l==n//2:
break
print(Ans)
``` | instruction | 0 | 67,336 | 0 | 134,672 |
No | output | 1 | 67,336 | 0 | 134,673 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s = input()
sa = s.count("a")
sb = s.count("b")
sc = s.count("c")
l = 0
lb = 0
r = len(s)-1
rb = len(s)-1
ans = []
maxi = "a"
while l < r:
while s[l] != "a" and l < r:
l += 1
while s[r] != "a" and l < r:
r -= 1
templ = s[lb:l]
tempr = s[r+1:rb+1]
bcount = min(templ.count("b"), tempr.count("b"))
ccount = min(templ.count("c"), tempr.count("c"))
if bcount > ccount:
ans.append("b"*bcount)
else:
ans.append("c"*ccount)
if l < r:
ans.append("a")
l += 1
r -= 1
lb = l
rb = r
if s.count(maxi) % 2 == 0:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp)
else:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp[1:])
ans = "".join(ans)
if len(ans) >= len(s)//2:
print(ans)
else:
l = 0
lb = 0
r = len(s)-1
rb = len(s)-1
ans = []
maxi = "b"
while l < r:
while s[l] != "b" and l < r:
l += 1
while s[r] != "b" and l < r:
r -= 1
templ = s[lb:l]
tempr = s[r+1:rb+1]
bcount = min(templ.count("c"), tempr.count("c"))
ccount = min(templ.count("a"), tempr.count("a"))
if bcount > ccount:
ans.append("c"*bcount)
else:
ans.append("a"*ccount)
if l < r:
ans.append("b")
l += 1
r -= 1
lb = l
rb = r
if s.count(maxi) % 2 == 0:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp)
else:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp[1:])
ans = "".join(ans)
if len(ans) >= len(s)//2:
print(ans)
else:
l = 0
lb = 0
r = len(s)-1
rb = len(s)-1
ans = []
maxi = "c"
while l < r:
while s[l] != "c" and l < r:
l += 1
while s[r] != "c" and l < r:
r -= 1
templ = s[lb:l]
tempr = s[r+1:rb+1]
bcount = min(templ.count("a"), tempr.count("a"))
ccount = min(templ.count("b"), tempr.count("b"))
if bcount > ccount:
ans.append("a"*bcount)
else:
ans.append("b"*ccount)
if l < r:
ans.append("c")
l += 1
r -= 1
lb = l
rb = r
if s.count(maxi) % 2 == 0:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp)
else:
anstemp = ans[:]
anstemp.reverse()
ans.extend(anstemp[1:])
ans = "".join(ans)
if len(ans) >= len(s)//2:
print(ans)
else:
if len(s) <= 3:
print(s[0])
else:
print("IMPOSSIBLE")
``` | instruction | 0 | 67,337 | 0 | 134,674 |
No | output | 1 | 67,337 | 0 | 134,675 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s=input()
ss=s[::-1]
n=len(s)
DP=[[""]*(n+1) for _ in range(n+1)]
for i in range(n):
for j in range(n):
if s[i]==ss[j]:
DP[i+1][j+1]=DP[i][j]+s[i]
else:
if len(DP[i+1][j])>=len(DP[i][j+1]):
DP[i+1][j+1]=DP[i+1][j]
else:
DP[i+1][j+1]=DP[i][j+1]
if len(DP[n][n])>=n/2:
print(DP[n][n])
else:
"IMPOSSIBLE"
``` | instruction | 0 | 67,338 | 0 | 134,676 |
No | output | 1 | 67,338 | 0 | 134,677 |
Evaluate the correctness of the submitted Python 3 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
s = input()
out = []
for i in range(0, len(s) // 2-2, 2):
cntA = len(list(filter(lambda x: x == 'a', [s[i], s[i+1], s[-(i+1)], s[-(i+2)]])))
cntB = len(list(filter(lambda x: x == 'b', [s[i], s[i+1], s[-(i+1)], s[-(i+2)]])))
cntC = len(list(filter(lambda x: x == 'c', [s[i], s[i+1], s[-(i+1)], s[-(i+2)]])))
if cntA > 1:
out.append('a')
elif cntB > 1:
out.append('b')
else:
out.append('c')
print("".join(out), s[len(s) // 2], "".join(reversed(out)), sep="")
``` | instruction | 0 | 67,339 | 0 | 134,678 |
No | output | 1 | 67,339 | 0 | 134,679 |
Evaluate the correctness of the submitted Python 2 solution to the coding contest problem. Provide a "Yes" or "No" response.
Alice bought a Congo Prime Video subscription and was watching a documentary on the archaeological findings from Factor's Island on Loch Katrine in Scotland. The archaeologists found a book whose age and origin are unknown. Perhaps Alice can make some sense of it?
The book contains a single string of characters "a", "b" and "c". It has been pointed out that no two consecutive characters are the same. It has also been conjectured that the string contains an unusually long subsequence that reads the same from both sides.
Help Alice verify this by finding such subsequence that contains at least half of the characters of the original string, rounded down. Note that you don't have to maximise the length of it.
A string a is a subsequence of a string b if a can be obtained from b by deletion of several (possibly, zero or all) characters.
Input
The input consists of a single string s (2 ≤ |s| ≤ 10^6). The string s consists only of characters "a", "b", "c". It is guaranteed that no two consecutive characters are equal.
Output
Output a palindrome t that is a subsequence of s and |t| ≥ ⌊ (|s|)/(2) ⌋.
If there are multiple solutions, you may print any of them. You don't have to maximise the length of t.
If there are no solutions, output a string "IMPOSSIBLE" (quotes for clarity).
Examples
Input
cacbac
Output
aba
Input
abc
Output
a
Input
cbacacacbcbababacbcb
Output
cbaaacbcaaabc
Note
In the first example, other valid answers include "cacac", "caac", "aca" and "ccc".
Submitted Solution:
```
from sys import stdin, stdout
from collections import Counter, defaultdict
from itertools import permutations, combinations
raw_input = stdin.readline
pr = stdout.write
def in_num():
return int(raw_input())
def in_arr():
return map(int,raw_input().split())
def pr_num(n):
stdout.write(str(n)+'\n')
def pr_arr(arr):
pr(' '.join(map(str,arr))+'\n')
# fast read function for total integer input
def inp():
# this function returns whole input of
# space/line seperated integers
# Use Ctrl+D to flush stdin.
return map(int,stdin.read().split())
range = xrange # not for python 3.0+
# main code
r=raw_input()
n=len(r)
l1=0
r1=n-1
ans=[]
while r1-l1>2:
if r[l1]==r[r1]:
ans.append(r[l1])
l1+=1
r1-=1
elif r[l1]==r[r1-1]:
ans.append(r[l1])
l1+=1
r1-=2
elif r[l1+1]==r[r1]:
ans.append(r[l1+1])
l1+=2
r1-=1
else:
ans.append(r[l1+1])
l1+=2
r1-=2
if r1>=l1:
ans.append(r[l1])
ans=''.join(ans)
pr(ans+''.join(reversed(ans[:-1])))
``` | instruction | 0 | 67,340 | 0 | 134,680 |
No | output | 1 | 67,340 | 0 | 134,681 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,341 | 0 | 134,682 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
def naiveSolve():
return
def getMinChanges(s,t,n,k):
arr=[0]*n
for i in range(n):
if s[i]!=t[i]:
arr[i]=1
p=arr
for i in range(1,n):
p[i]+=p[i-1]
def query(l,r):
res=p[r]
if l-1>=0: res-=p[l-1]
return res
ans=inf
for l in range(n):
r=l+k-1
if r==n:
break
ans=min(ans,query(l,r))
return ans
def main():
q=int(input())
allans=[]
for _ in range(q):
n,k=readIntArr()
s=input()
ans=inf
m=(n+2)//3
testStrings=[('RGB'*m)[:n],('GBR'*m)[:n],('BRG'*m)[:n]]
for t in testStrings:
ans=min(ans,getMinChanges(s,t,n,k))
allans.append(ans)
multiLineArrayPrint(allans)
return
import sys
# input=sys.stdin.buffer.readline #FOR READING PURE INTEGER INPUTS (space separation ok)
input=lambda: sys.stdin.readline().rstrip("\r\n") #FOR READING STRING/TEXT INPUTS.
def oneLineArrayPrint(arr):
print(' '.join([str(x) for x in arr]))
def multiLineArrayPrint(arr):
print('\n'.join([str(x) for x in arr]))
def multiLineArrayOfArraysPrint(arr):
print('\n'.join([' '.join([str(x) for x in y]) for y in arr]))
def readIntArr():
return [int(x) for x in input().split()]
# def readFloatArr():
# return [float(x) for x in input().split()]
def makeArr(defaultValFactory,dimensionArr): # eg. makeArr(lambda:0,[n,m])
dv=defaultValFactory;da=dimensionArr
if len(da)==1:return [dv() for _ in range(da[0])]
else:return [makeArr(dv,da[1:]) for _ in range(da[0])]
def queryInteractive(l,r):
print('? {} {}'.format(l,r))
sys.stdout.flush()
return int(input())
def answerInteractive(x):
print('! {}'.format(x))
sys.stdout.flush()
inf=float('inf')
MOD=10**9+7
# MOD=998244353
from math import gcd,floor,ceil
for _abc in range(1):
main()
``` | output | 1 | 67,341 | 0 | 134,683 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,342 | 0 | 134,684 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
import sys
import math
q = int(sys.stdin.readline())
for _ in range(q):
n, k = map(int, sys.stdin.readline().split())
sub = sys.stdin.readline().strip()
ori = ['RGB', 'GBR', 'BRG']
minVal = sys.maxsize
for i in range(3):
cnt = 0
for j in range(k):
if sub[j] != ori[i][j % 3]:
cnt += 1
st = 1
end = k
minVal = min(minVal, cnt)
if n == k:
pass
else:
for j in range(n):
if sub[st-1] != ori[i][(st-1) % 3]:
cnt -= 1
if sub[end] != ori[i][end % 3]:
cnt += 1
minVal = min(minVal, cnt)
if end == len(sub) - 1:
break
st += 1
end += 1
print(minVal)
``` | output | 1 | 67,342 | 0 | 134,685 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,343 | 0 | 134,686 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
import sys
def process(S, k, n):
if k==1:
return 0
answer = float('inf')
current = [0, 0, 0]
indexes = {'R': 0, 'G': 1, 'B': 2}
for i in range(k):
c = chr(S[i])
index = (indexes[c]-i) % 3
for j in range(3):
current[j]+=1
current[index]-=1
answer = min(answer, min(current))
for i in range(k, n):
c1 = chr(S[i-k])
index1 = (indexes[c1]-i+k) % 3
for j in range(3):
current[j]-=1
current[index1]+=1
c = chr(S[i])
index = (indexes[c]-i) % 3
for j in range(3):
current[j]+=1
current[index]-=1
answer = min(answer, min(current))
return answer
input = sys.stdin.buffer.readline
t = int(input())
for i in range(t):
n, k = [int(x) for x in input().split()]
S = input()
# print(S)
if k==1:
print(0)
else:
print(process(S, k, n))
``` | output | 1 | 67,343 | 0 | 134,687 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,344 | 0 | 134,688 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
import sys
input = sys.stdin.readline
Q = int(input())
D = {"R":0, "G":1, "B":2}
for _ in range(Q):
N, K = map(int, input().split())
S = input()
mi = K
for i in range(3):
d = 0
for j in range(N):
if D[S[j]] != (i+j) % 3:
d += 1
if j >= K and D[S[j-K]] != (i+j-K) % 3:
d -= 1
if j >= K-1:
mi = min(mi, d)
print(mi)
``` | output | 1 | 67,344 | 0 | 134,689 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,345 | 0 | 134,690 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
t = int(input())
for _ in range(t):
n,k = map(int,input().split())
s = input()
if(n==1): print(0);continue
A1 = "RGB"*n
A2 = "GBR"*n
A3 = "BRG"*n
ans = k
x1 = 0
x2 =0
x3 =0
for j in range(0,k):
x1+=s[j]!=A1[j]
x2+=s[j]!=A2[j]
x3+=s[j]!=A3[j]
ans = min(ans,x1,x2,x3)
for i in range(k,n):
x1+=(s[i]!=A1[i])-(s[i-k]!=A1[i-k])
x2+=(s[i]!=A2[i])-(s[i-k]!=A2[i-k])
x3+=(s[i]!=A3[i])-(s[i-k]!=A3[i-k])
ans = min(ans,x1,x2,x3)
print(ans)
``` | output | 1 | 67,345 | 0 | 134,691 |
Provide tags and a correct Python 3 solution for this coding contest problem.
The only difference between easy and hard versions is the size of the input.
You are given a string s consisting of n characters, each character is 'R', 'G' or 'B'.
You are also given an integer k. Your task is to change the minimum number of characters in the initial string s so that after the changes there will be a string of length k that is a substring of s, and is also a substring of the infinite string "RGBRGBRGB ...".
A string a is a substring of string b if there exists a positive integer i such that a_1 = b_i, a_2 = b_{i + 1}, a_3 = b_{i + 2}, ..., a_{|a|} = b_{i + |a| - 1}. For example, strings "GBRG", "B", "BR" are substrings of the infinite string "RGBRGBRGB ..." while "GR", "RGR" and "GGG" are not.
You have to answer q independent queries.
Input
The first line of the input contains one integer q (1 ≤ q ≤ 2 ⋅ 10^5) — the number of queries. Then q queries follow.
The first line of the query contains two integers n and k (1 ≤ k ≤ n ≤ 2 ⋅ 10^5) — the length of the string s and the length of the substring.
The second line of the query contains a string s consisting of n characters 'R', 'G' and 'B'.
It is guaranteed that the sum of n over all queries does not exceed 2 ⋅ 10^5 (∑ n ≤ 2 ⋅ 10^5).
Output
For each query print one integer — the minimum number of characters you need to change in the initial string s so that after changing there will be a substring of length k in s that is also a substring of the infinite string "RGBRGBRGB ...".
Example
Input
3
5 2
BGGGG
5 3
RBRGR
5 5
BBBRR
Output
1
0
3
Note
In the first example, you can change the first character to 'R' and obtain the substring "RG", or change the second character to 'R' and obtain "BR", or change the third, fourth or fifth character to 'B' and obtain "GB".
In the second example, the substring is "BRG". | instruction | 0 | 67,346 | 0 | 134,692 |
Tags: data structures, dp, implementation, two pointers
Correct Solution:
```
def main():
q = int(input())
ans = []
for i in range(q):
n, k = map(int, input().split())
s = input()
min_ans = 10 ** 9
pr1 = [0]
pr2 = [0]
pr3 = [0]
for i in range(n):
count1 = 0
count2 = 0
count3 = 0
if i % 3 == 0:
if s[i] != "R":
count1 += 1
if s[i] != "G":
count2 += 1
if s[i] != "B":
count3 += 1
if i % 3 == 1:
if s[i] != "G":
count1 += 1
if s[i] != "B":
count2 += 1
if s[i] != "R":
count3 += 1
if i % 3 == 2:
if s[i] != "B":
count1 += 1
if s[i] != "R":
count2 += 1
if s[i] != "G":
count3 += 1
pr1.append(pr1[-1] + count1)
pr2.append(pr2[-1] + count2)
pr3.append(pr3[-1] + count3)
j = i + 1
if j >= k:
count1 = pr1[j] - pr1[j - k]
count2 = pr2[j] - pr2[j - k]
count3 = pr3[j] - pr3[j - k]
min_ans = min(min_ans, count1, count2, count3)
ans.append(min_ans)
print(*ans, sep="\n")
main()
``` | output | 1 | 67,346 | 0 | 134,693 |
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