text stringlengths 37 1.41M |
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'''
-Medium-
*DFS*
*Union Find*
You are given a positive integer n representing n cities numbered from 1 to n. You are also given a 2D array roads where roads[i] = [ai, bi, distancei] indicates that there is a bidirectional road between cities ai and bi with a distance equal to distancei. The cities graph is not nece... |
'''
-Medium-
Given an array of integers nums and an integer k. A continuous subarray is called nice if
there are k odd numbers on it.
Return the number of nice sub-arrays.
Example 1:
Input: nums = [1,1,2,1,1], k = 3
Output: 2
Explanation: The only sub-arrays with 3 odd numbers are [1,1,2,1] and [1,2,1,1].
Examp... |
'''
-Hard-
You want to form a target string of lowercase letters.
At the beginning, your sequence is target.length '?' marks. You also have a stamp of
lowercase letters.
On each turn, you may place the stamp over the sequence, and replace every letter in the
sequence with the corresponding letter from the stamp. ... |
'''
-Medium-
*Array*
*Two Pointers*
Let's call any (contiguous) subarray B (of A) a valley if the following
properties hold:
B.length >= 3
There exists some 0 < i < B.length - 1 such that B[0] > B[1] > ... B[i-1]
> B[i] < B[i+1] < ... < B[B.length - 1]
(Note that B could be any subarray of A, including the entire a... |
'''
Given an array of integers nums and an integer k, return the number of unique
k-diff pairs in the array.
A k-diff pair is an integer pair (nums[i], nums[j]), where the following are true:
0 <= i, j < nums.length
i != j
a <= b
b - a == k
Example 1:
Input: nums = [3,1,4,1,5], k = 2
Output: 2
Explanation: There ... |
'''
-Hard-
*DP*
*Memoization*
*Bitmask*
*Bipartite*
Given a m * n matrix seats that represent seats distributions in a classroom.
If a seat is broken, it is denoted by '#' character otherwise it is denoted
by a '.' character.
Students can see the answers of those sitting next to the left, right, upper
left and upp... |
'''
-Medium-
For a stream of integers, implement a data structure that checks if the last k integers parsed in the stream are equal to value.
Implement the DataStream class:
DataStream(int value, int k) Initializes the object with an empty integer stream and the two integers value and k.
boolean consec(int num) Ad... |
'''
-Medium-
You are given two non-increasing 0-indexed integer arrays nums1 and nums2.
A pair of indices (i, j), where 0 <= i < nums1.length and 0 <= j < nums2.length, is
valid if both i <= j and nums1[i] <= nums2[j]. The distance of the pair is j - i.
Return the maximum distance of any valid pai... |
'''
-Medium-
*GCD*
*Sorting*
ou are given a 2D integer array stockPrices where stockPrices[i] = [dayi, pricei] indicates the price of the stock on day dayi is pricei. A line chart is created from the array by plotting the points on an XY plane with the X-axis representing the day and the Y-axis representing the price ... |
'''
-Hard-
You are given a 0-indexed integer array nums of length n.
A split at an index i where 0 <= i <= n - 2 is called valid if the product of the first i + 1 elements and the product of the remaining elements are coprime.
For example, if nums = [2, 3, 3], then a split at the index i = 0 is valid because 2 and ... |
'''
-Medium-
Given an integer n, return the count of all numbers with unique digits, x, where 0 <= x < 10n.
Example 1:
Input: n = 2
Output: 91
Explanation: The answer should be the total numbers in the range of 0 ≤ x < 100, excluding 11,22,33,44,55,66,77,88,99
Example 2:
Input: n = 0
Output: 1
Constraints:
0... |
'''
-Medium-
You are given a 0-indexed integer array nums.
The effective value of three indices i, j, and k is defined as ((nums[i] | nums[j]) & nums[k]).
The xor-beauty of the array is the XORing of the effective values of all the possible triplets of indices (i, j, k) where 0 <= i, j, k < n.
Return the xor-beaut... |
'''
-Medium-
You are given a 0-indexed integer array nums of length n. You are initially standing
at index 0. You can jump from index i to index j where i < j if:
nums[i] <= nums[j] and nums[k] < nums[i] for all indexes k in the range i < k < j, or
nums[i] > nums[j] and nums[k] >= nums[i] for all indexes k in the r... |
'''
-Medium-
*Stack*
Design a max stack that supports push, pop, top, peekMax and popMax.
push(x) -- Push element x onto stack.
pop() -- Remove the element on top of the stack and return it.
top() -- Get the element on the top.
peekMax() -- Retrieve the maximum element in the stack.
popMax() -- Retrieve the maxim... |
'''
-Hard-
*Fenwick Tree*
Given an integer array instructions, you are asked to create a sorted array
from the elements in instructions. You start with an empty container nums.
For each element from left to right in instructions, insert it into nums.
The cost of each insertion is the minimum of the following:
The ... |
'''
-Hard-
$$$
*Sliding Window*
You are given an integer array nums and a positive integer k.
The frequency score of an array is the sum of the distinct values in the array raised to the power of their frequencies, taking the sum modulo 109 + 7.
For example, the frequency score of the array [5,4,5,7,4,4] is (43 + ... |
'''
-Hard-
*Kadane's Algorithm*
You are given two 0-indexed integer arrays nums1 and nums2, both of length n.
You can choose two integers left and right where 0 <= left <= right < n and swap the subarray nums1[left...right] with the subarray nums2[left...right].
For example, if nums1 = [1,2,3,4,5] and nums2 = [11,1... |
'''
-Hard-
There is a long and thin painting that can be represented by a number line.
You are given a 0-indexed 2D integer array paint of length n, where
paint[i] = [starti, endi]. This means that on the ith day you need to paint
the area between starti and endi.
Painting the same area multiple times will create... |
'''
-Medium-
*BFS*
*DFS*
*Memoization*
Given a string s and a set of n substrings. You are supposed to remove every instance of
those n substrings from s so that s is of the minimum length and output this minimum length.
样例
Example 1:
Input:
"ccdaabcdbb"
["ab","cd"]
Output:
2
Explanation:
ccdaabcdbb -> ccdacdbb... |
'''
-Medium-
You are given an array of logs. Each log is a space-delimited string of words, where the first word is the identifier.
There are two types of logs:
Letter-logs: All words (except the identifier) consist of lowercase English letters.
Digit-logs: All words (except the identifier) consist of digits.
Reord... |
'''
-Medium-
*GCD*
*Hash Table*
You are given n rectangles represented by a 0-indexed 2D integer array rectangles, where rectangles[i] = [widthi, heighti] denotes the width and height of the ith rectangle.
Two rectangles i and j (i < j) are considered interchangeable if they have the same width-to-height ratio. More... |
'''
-Medium-
$$$
*Monotonic Stack*
*Recursion*
You are given a 0-indexed integer array order of length n, a permutation of integers from 1 to n representing the order of insertion into a binary search tree.
A binary search tree is defined as follows:
<li>The left subtree of a node contains only nodes with keys <str... |
'''
-Medium-
$$$
*Sorting*
You are given an integer n which is the length of a 0-indexed array nums, and a 0-indexed 2D-array ranges, which is a list of sub-ranges of nums (sub-ranges may overlap).
Each row ranges[i] has exactly 2 cells:
ranges[i][0], which shows the start of the ith range (inclusive)
ranges[i][1], ... |
'''
-Easy-
The count-and-say sequence is a sequence of digit strings defined by the recursive
formula:
countAndSay(1) = "1"
countAndSay(n) is the way you would "say" the digit string from countAndSay(n-1),
which is then converted into a different digit string.
To determine how you "say" a digit string, split it int... |
'''
-Medium-
Given an integer array nums of size n, return the minimum number of moves required
to make all array elements equal.
In one move, you can increment or decrement an element of the array by 1.
Example 1:
Input: nums = [1,2,3]
Output: 2
Explanation:
Only two moves are needed (remember each move incre... |
'''
-Medium-
*Auxiliary Array*
You are given a 0-indexed integer array nums of size n and a positive integer k.
We call an index i in the range k <= i < n - k good if the following conditions are satisfied:
The k elements that are just before the index i are in non-increasing order.
The k elements that are just af... |
'''
-Easy-
Given an integer columnNumber, return its corresponding column title as
it appears in an Excel sheet.
For example:
A -> 1
B -> 2
C -> 3
...
Z -> 26
AA -> 27
AB -> 28
...
Example 1:
Input: columnNumber = 1
Output: "A"
Example 2:
Input: columnNumber = 28
Output: "AB"
Example 3:
Input: columnNumber =... |
'''
-Medium-
Design a data structure that is initialized with a list of different words. Provided a string,
you should determine if you can change exactly one character in this string to match any word
in the data structure.
Implement the MagicDictionary class:
MagicDictionary() Initializes the object.
void buildD... |
'''
You are given a list of non-negative integers, a1, a2, ..., an, and a target,
S. Now you have 2 symbols + and -. For each integer, you should choose one
from + and - as its new symbol.
Find out how many ways to assign symbols to make sum of integers equal to
target S.
Example 1:
Input: nums is [1, 1, 1, 1, 1]... |
'''
-Medium-
There are 8 prison cells in a row and each cell is either occupied or vacant.
Each day, whether the cell is occupied or vacant changes according to the following rules:
If a cell has two adjacent neighbors that are both occupied or both vacant, then the cell
becomes occupied.
Otherwise, it becomes vac... |
'''
-Medium-
Given a string s and an array of integers cost where cost[i] is the cost of
deleting the ith character in s.
Return the minimum cost of deletions such that there are no two identical
letters next to each other.
Notice that you will delete the chosen characters at the same time, in other
words, after ... |
'''
-Medium-
Alice plays the following game, loosely based on the card game "21".
Alice starts with 0 points and draws numbers while she has less than k points.
During each draw, she gains an integer number of points randomly from
the range [1, maxPts], where maxPts is an integer. Each draw is independent
and the... |
'''
-Hard-
Given a data stream input of non-negative integers a1, a2, ..., an, ...,
summarize the numbers seen so far as a list of disjoint intervals.
For example, suppose the integers from the data stream are 1, 3, 7, 2, 6, ...,
then the summary will be:
[1, 1]
[1, 1], [3, 3]
[1, 1], [3, 3], [7, 7]
[1, 3], [7, 7]... |
'''
-Medium-
Given a string s, return the maximum number of ocurrences of any
substring under the following rules:
The number of unique characters in the substring must be less
than or equal to maxLetters.
The substring size must be between minSize and maxSize inclusive.
Example 1:
Input: s = "aababcaab", maxL... |
'''
-Easy-
Given three integer arrays arr1, arr2 and arr3 sorted in strictly increasing order,
return a sorted array of only the integers that appeared in all three arrays.
Example 1:
Input: arr1 = [1,2,3,4,5], arr2 = [1,2,5,7,9], arr3 = [1,3,4,5,8]
Output: [1,5]
Explanation: Only 1 and 5 appeared in the three a... |
# -*- coding: utf-8 -*-
"""
Created on Sun Jun 25 14:20:26 2017
@author: merli
"""
class Solution(object):
def insertAtBottom(self, s, ele):
if s:
tmp = s.pop()
self.insertAtBottom(s, ele)
s.append(tmp)
else:
s.append(ele)
def reverseStack... |
'''
-Medium-
Alice and Bob continue their games with stones. There is a row of n stones, and each stone has an associated value. You are given an integer array stones, where stones[i] is the value of the ith stone.
Alice and Bob take turns, with Alice starting first. On each turn, the player may remove any stone from... |
'''
-Medium-
Given a string s, return the number of unique palindromes of length three that are a subsequence of s.
Note that even if there are multiple ways to obtain the same subsequence, it is still only counted once.
A palindrome is a string that reads the same forwards and backwards.
A subsequence of a string ... |
'''
-Medium-
*Sorting*
*Greedy*
You are given an array of positive integers arr. Perform some operations (possibly none) on arr so that it satisfies these conditions:
The value of the first element in arr must be 1.
The absolute difference between any 2 adjacent elements must be less than or equal to 1. In other wor... |
'''
-Medium-
*Difference Array*
You are given a string s of lowercase English letters and a 2D integer array shifts where shifts[i] = [starti, endi, directioni]. For every i, shift the characters in s from the index starti to the index endi (inclusive) forward if directioni = 1, or shift the characters backward if dir... |
'''
-Medium-
You are given a directed graph with n nodes labeled from 0 to n - 1, where each node has exactly one outgoing edge.
The graph is represented by a given 0-indexed integer array edges of length n, where edges[i] indicates that there is a directed edge from node i to node edges[i].
The edge score of a node... |
'''
-Hard-
Given an array of digits, you can write numbers using each digits[i] as many
times as we want. For example, if digits = ['1','3','5'], we may write
numbers such as '13', '551', and '1351315'.
Return the number of positive integers that can be generated that are less
than or equal to a given integer n.
... |
'''
-Medium-
*DFS*
There is an undirected tree with n nodes labeled from 0 to n - 1 and n - 1 edges.
You are given a 2D integer array edges of length n - 1 where edges[i] = [ai, bi] indicates that there is an edge between nodes ai and bi in the tree. You are also given an integer array restricted which represents r... |
'''
-Hard-
*Couting*
*DP*
*Digit DP*
*Bitmask*
We call a positive integer special if all of its digits are distinct.
Given a positive integer n, return the number of special integers that belong to the interval [1, n].
Example 1:
Input: n = 20
Output: 19
Explanation: All the integers from 1 to 20, except 11, ar... |
'''
-Medium-
*Dijkstra's Algorithm*
$$$
You are given a positive integer n representing n cities numbered from 1 to n. You are also given a 2D array roads, where roads[i] = [ai, bi, costi] indicates that there is a bidirectional road between cities ai and bi with a cost of traveling equal to costi.
You can buy app... |
'''
-Hard-
*Stack*
*Monotonic Queue*
Given n non-negative integers representing the histogram's bar height where
the width of each bar is 1, find the area of largest rectangle in the
histogram.
Example:
Input: [2,1,5,6,2,3]
Output: 10
'''
class Solution(object):
def largestRectangleArea(self, heights):
... |
'''
-Medium-
Design your implementation of the linked list. You can choose to use a singly or doubly linked list.
A node in a singly linked list should have two attributes: val and next. val is the value of the current node, and next is a pointer/reference to the next node.
If you want to use the doubly linked list,... |
'''
-Medium-
In LeetCode Store, there are n items to sell. Each item has a price. However, there are
some special offers, and a special offer consists of one or more different kinds of items
with a sale price.
You are given an integer array price where price[i] is the price of the ith item, and an
integer array nee... |
'''
-Medium-
Suppose you are at a party with n people (labeled from 0 to n - 1) and among them,
there may exist one celebrity. The definition of a celebrity is that all the
other n - 1 people know him/her but he/she does not know any of them.
Now you want to find out who the celebrity is or verify that there is not... |
'''
-Medium-
Given a string s and an integer k, return true if you can use all the characters in s to construct k palindrome strings or false otherwise.
Example 1:
Input: s = "annabelle", k = 2
Output: true
Explanation: You can construct two palindromes using all characters in s.
Some possible constructions "ann... |
'''
-Medium-
There is a bookstore owner that has a store open for n minutes. Every minute, some number of customers
enter the store. You are given an integer array customers of length n where customers[i] is the number
of the customer that enters the store at the start of the ith minute and all those customers leave... |
'''
-Medium-
*Greedy*
*Priority Queue*
There is a special kind of apple tree that grows apples every day for n days.
On the ith day, the tree grows apples[i] apples that will rot after days[i] days,
that is on day i + days[i] the apples will be rotten and cannot be eaten.
On some days, the apple tree does not grow ... |
'''
-Medium-
*Binary Search*
You are given a 0-indexed integer array candies. Each element in the array denotes
a pile of candies of size candies[i]. You can divide each pile into any number
of sub piles, but you cannot merge two piles together.
You are also given an integer k. You should allocate piles of candie... |
'''
-Medium-
*Sliding Window*
You are given an array nums consisting of positive integers.
We call a subarray of an array complete if the following condition is satisfied:
The number of distinct elements in the subarray is equal to the number of distinct elements in the whole array.
Return the number of complete suba... |
'''
-Medium-
Design a data structure that takes an array of integers. Write a method that
finds the position of the element with the minimum value between two given indices.
'''
import math
class RMQ(object):
# Sparse Table (ST) Algorithm
# O(NlogN) to construct ST table
def __init__(self, nums):
... |
'''
-Medium-
*Greedy*
*Backtracking*
You are given a 0-indexed string pattern of length n consisting of the characters 'I' meaning increasing and 'D' meaning decreasing.
A 0-indexed string num of length n + 1 is created using the following conditions:
num consists of the digits '1' to '9', where each digit is used a... |
'''
-Medium-
An integer n is strictly palindromic if, for every base b between 2 and n - 2 (inclusive), the string representation of the integer n in base b is palindromic.
Given an integer n, return true if n is strictly palindromic and false otherwise.
A string is palindromic if it reads the same forward and backw... |
'''
-Hard-
*DP*
*Greedy*
Given an input string (s) and a pattern (p), implement wildcard pattern matching
with support for '?' and '*' where:
'?' Matches any single character.
'*' Matches any sequence of characters (including the empty sequence).
The matching should cover the entire input string (not partial).
... |
'''
-Easy-
You are given two strings s1 and s2 of equal length. A string swap is an
operation where you choose two indices in a string (not necessarily different)
and swap the characters at these indices.
Return true if it is possible to make both strings equal by performing at most
one string swap on exactly one... |
'''
-Medium-
A complete binary tree is a binary tree in which every level, except possibly the last, is completely filled, and all nodes are as far left as possible.
Design an algorithm to insert a new node to a complete binary tree keeping it complete after the insertion.
Implement the CBTInserter class:
CBTInser... |
'''
-Medium-
Given a binary tree root and an integer target, delete all the leaf nodes with value target.
Note that once you delete a leaf node with value target, if its parent node becomes a leaf node and has the value target, it should also be deleted (you need to continue doing that until you cannot).
Example... |
'''
-Medium-
*DP*
*Stack*
You are given a string s consisting only of characters 'a' and 'b'.
You can delete any number of characters in s to make s balanced. s is balanced if there is no pair of indices (i,j) such that i < j and s[i] = 'b' and s[j]= 'a'.
Return the minimum number of deletions needed to make ... |
'''
-Easy-
Given an array A of strings made only from lowercase letters, return a
list of all characters that show up in all strings within the list
(including duplicates). For example, if a character occurs 3 times
in all strings but not 4 times, you need to include that character three
times in the final answe... |
'''
-Medium-
Given a binary search tree and a node in it, find the in-order successor of that node in the BST.
Note: If the given node has no in-order successor in the tree, return null.
Example 1:
Input: root = [2,1,3], p = 1
2
/ \
1 3
Output: 2
Example 2:
Input: root = [5,3,6,2,4,null,null,1], p = 6
... |
'''
-Hard-
*BFS*
*Dijkstra's Algorithm*
You are given a 0-indexed 2D integer array grid of size m x n. Each cell has one of two values:
0 represents an empty cell,
1 represents an obstacle that may be removed.
You can move up, down, left, or right from and to an empty cell.
Return the minimum number of obstacles to r... |
'''
-Hard-
Given a string num that contains only digits and an integer target, return all possibilities
to add the binary operators '+', '-', or '*' between the digits of num so that the resultant
expression evaluates to the target value.
Example 1:
Input: num = "123", target = 6
Output: ["1*2*3","1+2+3"]
Examp... |
'''
-Medium-
$$$
There is an undirected connected tree with n nodes labeled from 1 to n and n - 1 edges. You are given the integer n. The parent node of a node with a label v is the node with the label floor (v / 2). The root of the tree is the node with the label 1.
For example, if n = 7, then the node with the la... |
'''
-Easy-
Given an array nums of n integers where nums[i] is in the range [1, n], return an array of all the
integers in the range [1, n] that do not appear in nums.
Example 1:
Input: nums = [4,3,2,7,8,2,3,1]
Output: [5,6]
Example 2:
Input: nums = [1,1]
Output: [2]
Constraints:
n == nums.length
1 <= n <= ... |
'''
-Medium-
There are n computers numbered from 0 to n-1 connected by ethernet cables
connections forming a network where connections[i] = [a, b] represents a
connection between computers a and b. Any computer can reach any other
computer directly or indirectly through the network.
Given an initial computer netw... |
'''
Given an array nums, we call (i, j) an important reverse pair if i < j
and nums[i] > 2*nums[j].
You need to return the number of important reverse pairs in the given array.
Example1:
Input: [1,3,2,3,1]
Output: 2
Example2:
Input: [2,4,3,5,1]
Output: 3
Note:
The length of the given array will not exceed 50,000.... |
'''
-Medium-
In a given 2D binary array grid, there are two islands. (An island
is a 4-directionally connected group of 1s not connected to any other 1's.)
Now, we may change 0s to 1s so as to connect the two islands together
to form 1 island.
Return the smallest number of 0s that must be flipped. (It is guaran... |
'''
-Medium-
$$$
*Two Pointers*
*Greedy*
You are given an array nums consisting of positive integers.
You can perform the following operation on the array any number of times:
Choose any two adjacent elements and replace them with their sum.
For example, if nums = [1,2,3,1], you can apply one operation to make it [... |
'''
-Medium-
We had some 2-dimensional coordinates, like "(1, 3)" or "(2, 0.5)". Then, we removed all commas,
decimal points, and spaces, and ended up with the string s. Return a list of strings representing
all possibilities for what our original coordinates could have been.
Our original representation never had... |
'''
-Medium-
Given a binary tree
struct Node {
int val;
Node *left;
Node *right;
Node *next;
}
Populate each next pointer to point to its next right node. If there is no next
right node, the next pointer should be set to NULL.
Initially, all next pointers are set to NULL.
Follow up:
You may only use co... |
'''
-Medium-
*DFS*
*BFS*
You are given a list of bombs. The range of a bomb is defined as the area where its effect can be felt. This area is in the shape of a circle with the center as the location of the bomb.
The bombs are represented by a 0-indexed 2D integer array bombs where bombs[i] = [xi, yi, ri]. xi and yi de... |
'''
-Medium-
*Sorting*
*Monotonic Stack*
You are playing a game that contains multiple characters, and each of the characters
has two main properties: attack and defense. You are given a 2D integer array properties
where properties[i] = [attacki, defensei] represents the properties of the ith
character in the game... |
'''
-Hard-
*Sliding Window*
*Monotonic Queue*
You have n robots. You are given two 0-indexed integer arrays, chargeTimes and runningCosts, both of length n. The ith robot costs chargeTimes[i] units to charge and costs runningCosts[i] units to run. You are also given an integer budget.
The total cost of running k ch... |
'''
-Medium-
Given a 0-indexed integer array nums, return the number of subarrays of nums having an even product.
Example 1:
Input: nums = [9,6,7,13]
Output: 6
Explanation: There are 6 subarrays with an even product:
- nums[0..1] = 9 * 6 = 54.
- nums[0..2] = 9 * 6 * 7 = 378.
- nums[0..3] = 9 * 6 * 7 * 13 = 4914... |
'''
-Hard-
*Greedy*
*GCD*
There exists an infinitely large grid. You are currently at point (1, 1), and you need to reach the point (targetX, targetY) using a finite number of steps.
In one step, you can move from point (x, y) to any one of the following points:
(x, y - x)
(x - y, y)
(2 * x, y)
(x, 2 * y)
Given two... |
'''
-Medium-
One way to serialize a binary tree is to use preorder traversal. When we encounter a non-null node,
we record the node's value. If it is a null node, we record using a sentinel value such as '#'.
For example, the above binary tree can be serialized to the string "9,3,4,#,#,1,#,#,2,#,6,#,#",
where '#' r... |
'''
-Hard-
*Hash Table*
Given an array nums of positive integers, return the longest possible length of
an array prefix of nums, such that it is possible to remove exactly one element
from this prefix so that every number that has appeared in it will have the same
number of occurrences.
If after removing one elem... |
'''
-Medium-
描述
Given a string, we can "shift" each of its letter to its successive letter, for example: "abc" -> "bcd".
We can keep "shifting" which forms the sequence:
"abc" -> "bcd" -> ... -> "xyz"
Given a list of strings which contains only lowercase alphabets, group all strings that belong to the
same shiftin... |
'''
-Easy-
Given two strings s and t, return true if s is a subsequence of t, or false otherwise.
A subsequence of a string is a new string that is formed from the original string by
deleting some (can be none) of the characters without disturbing the relative positions
of the remaining characters. (i.e., "ace" is ... |
'''
-Easy-
There is a bi-directional graph with n vertices, where each vertex is
labeled from 0 to n - 1 (inclusive). The edges in the graph are represented as a 2D integer array edges, where each edges[i] = [ui, vi] denotes a bi-directional edge between vertex ui and vertex vi. Every vertex pair is connected by at ... |
'''
Given an array of strings strs, group the anagrams together. You can return the
answer in any order.
An Anagram is a word or phrase formed by rearranging the letters of a different
word or phrase, typically using all the original letters exactly once.
Example 1:
Input: strs = ["eat","tea","tan","ate","nat",... |
'''
-Medium-
There is a regular convex polygon with n vertices. The vertices are labeled from 0 to n - 1 in a clockwise direction, and each vertex has exactly one monkey. The following figure shows a convex polygon of 6 vertices.
Each monkey moves simultaneously to a neighboring vertex. A neighboring vertex for a v... |
'''
-Medium-
Given the root of a perfect binary tree, reverse the node values at each odd level of the tree.
For example, suppose the node values at level 3 are [2,1,3,4,7,11,29,18], then it should become [18,29,11,7,4,3,1,2].
Return the root of the reversed tree.
A binary tree is perfect if all parent nodes have t... |
'''
-Easy-
*Queue*
Implement a last in first out (LIFO) stack using only two queues. The
implemented stack should support all the functions of a normal queue
(push, top, pop, and empty).
Implement the MyStack class:
void push(int x) Pushes element x to the top of the stack.
int pop() Removes the element on the top... |
'''
-Medium-
*Sorting*
Given an array of intervals intervals where intervals[i] = [starti, endi], return the minimum
number of intervals you need to remove to make the rest of the intervals non-overlapping.
Example 1:
Input: intervals = [[1,2],[2,3],[3,4],[1,3]]
Output: 1
Explanation: [1,3] can be removed and th... |
'''
-Easy-
*Prefix Sum*
Given a string s of zeros and ones, return the maximum score after splitting the string into two non-empty substrings (i.e. left substring and right substring).
The score after splitting a string is the number of zeros in the left substring plus the number of ones in the right substring.
E... |
'''
-Medium-
*Hash Table*
*Bijection*
Given a list of strings words and a string pattern, return a list of words[i]
that match pattern. You may return the answer in any order.
A word matches the pattern if there exists a permutation of letters p so that
after replacing every letter x in the pattern with p(x), we g... |
'''
-Medium-
You are given an integer array nums. The absolute sum of a subarray
[numsl, numsl+1, ..., numsr-1, numsr] is abs(numsl + numsl+1 + ... +
numsr-1 + numsr).
Return the maximum absolute sum of any (possibly empty) subarray of nums.
Note that abs(x) is defined as follows:
If x is a negative integer, then... |
'''
-Hard-
*Difference Array*
*Prefix Sum*
You are given an array nums. You can rotate it by a non-negative integer k so that the array
becomes [nums[k], nums[k + 1], ... nums[nums.length - 1], nums[0], nums[1], ..., nums[k-1]].
Afterward, any entries that are less than or equal to their index are worth one point.
... |
class Solution(object):
def knightDialer(self, N):
"""
:type N: int
:rtype: int
"""
moves={1:[8,6], 2:[7, 9], 3:[4,8],
4:[0,3,9], 5:[], 6:[0,1,7], 7:[2,6],
8:[1,3], 9:[2,4], 0:[4,6]}
#dp = [[set() for _ in range(N)] for _ in range(10)]
... |
'''
-Hard-
*KMP*
You are given two strings s and sub. You are also given a 2D character array mappings where mappings[i] = [oldi, newi] indicates that you may replace any number of oldi characters of sub with newi. Each character in sub cannot be replaced more than once.
Return true if it is possible to make sub a s... |
'''
-Medium-
描述
It's follow up problem for Binary Tree Longest Consecutive Sequence II
Given a k-ary tree, find the length of the longest consecutive sequence path.
The path could be start and end at any node in the tree
样例
Example 1:
Input:
5<6<7<>,5<>,8<>>,4<3<>,5<>,31<>>>
Output:
5
Explanation:
5
/ \
... |
'''
-Medium-
Given a string s, determine if it is valid.
A string s is valid if, starting with an empty string t = "", you can transform t into s after
performing the following operation any number of times:
Insert string "abc" into any position in t. More formally, t becomes tleft + "abc" + tright,
where t == tle... |
'''
-Medium-
In a garden represented as an infinite 2D grid, there is an apple tree planted at every integer coordinate. The apple tree planted at an integer coordinate (i, j) has |i| + |j| apples growing on it.
You will buy an axis-aligned square plot of land that is centered at (0, 0).
Given an integer neededAppl... |
'''
Given a string s, remove duplicate letters so that every letter appears once and
only once. You must make sure your result is the smallest in lexicographical order
among all possible results.
Note: This question is the same as 1081:
https://leetcode.com/problems/smallest-subsequence-of-distinct-characters/
... |
'''
-Medium-
Given two nodes of a binary tree p and q, return their lowest common ancestor (LCA).
Each node will have a reference to its parent node. The definition for Node is below:
class Node {
public int val;
public Node left;
public Node right;
public Node parent;
}
According to the definition ... |
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