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Checks Post Facto Description: Your university’s board game club just hosted a Checkers tournament, and you were assigned to take notes on the games. Unfortunately, while walking home, you dropped all of your papers into a puddle! Disaster! Much of what you wrote is now unreadable; all you have left ar...
26,800
Cheer Readers Description: The School Library Pep Squad is a squad of cheerleaders hoping to push the students in the library to study harder. There are $N$ cheerleaders in the squad, labeled from $1$ to $N$ for simplicity. To improve their routine, they decide to hold $Q$ after-school events for the ...
26,801
Cheering Game Description: One of the perhaps most important factors in deciding the winning team of a football match is the amount of cheers the teams get from their supporters. The Sportify football team is about to meet their worst opponent, Spoilify. As the manager of Sportify’s cheerleading squad,...
26,802
Cheese, If You Please Description: The “We Cut The Cheese” specialty food store sells specialized blendings of cheeses. For example, their Italian Blend is made up of $50\% $ provolone, $30\% $ mozzarella and $20\% $ parmesan, while their African Safari is made up of $74\% $ domiati, $25\% ...
26,803
Chemicals Monitoring Description: Victor works for Alberta Chemicals Monitoring (ACM). ACM is a company that analyses raw environmental data related to chemicals used in oil sand and other industries in Alberta, and produces some reports for environmental watchdogs. Victor is in charge of a multi-processo...
26,804
Chemist's vows Description: Chemist Clara swore a solemn vow—from now on, she can only speak atomic element symbols. Of course, this limits her ability to talk. She can say, for example, “I Am CLaRa” (as I is the symbol of iodine, Am is americium, C is carbon and so on). She can also say “InTeRnAtIONAl...
26,805
Chess Description: In chess the bishop is the chessman, which can only move diagonal. It is well known that bishops can reach only fields of one color but all of them in some number of moves (assuming no other figures are on the field). You are given two coordinates on a chess-field and should determin...
26,806
Chess Competition Description: In a chess competition, every player plays one game against every other player. The winner receives one point, the loser none. In case of a draw, both players receive half a point. When all games have been played, whoever scored the most points wins the competition. If mu...
26,807
Chess Tournament Description: Your friend is an organizer of the International Chess Playing Championship. He is worried that some of the contestants may be cheating, and he has asked you to help out. The chess players are allowed to report matches to the jury themselves, and this is not checked with t...
26,808
Chewbacca Description: You are given a tree of out-degree $K$ with $N$ nodes or, in other words, each node can have at most $K$ children. The tree is constructed so it is of the “lowest energy”: the nodes are placed in a new depth of the tree only when all the places (from left to right) in the previou...
26,809
Chicken Joggers Description: In the woods of Lill-Jansskogen, there is a network of trails that are often used by joggers. The trails have been much appreciated, and have been specially selected by the professors of the Royal Institute of Technology, enabling university students to take a short break f...
26,810
Chili COM Carne Description: Programmers all know COM, which is of course an abbreviation for Cost Of Maintenance and has no other interpretations. Often such costs can be lowered by automating certain tasks, but many programmers are overzealous in this regard and end up spending more time programming ...
26,811
Chinese Remainder Description: ## Input The first line of input consists of an integers $T$ where $1 \leq T \leq 1000$, the number of test cases. Then follow $T$ lines, each containing four integers $a$, $n$, $b$, $m$ satisfying $1 \leq n, m \leq 10^9$, $0 \leq a < n$, $0 \leq b < m$. Also, you may assume...
26,812
Chinese Remainder Theorem (non-relatively prime moduli) Description: ## Input The first line of input consists of an integers $T$ where $1 \leq T \leq 1000$, the number of test cases. Then follow $T$ lines, each containing four integers $a$, $n$, $b$, $m$ satisfying $1 \leq n, m \leq 10^9$, $0 \leq a < n$, $0...
26,813
Chocolate Balls Description: Bruno and Sofie are members of a mathematics club at their high school and go to a grocery store to buy snacks for their club meeting. When they were at the grocery store, they saw something incredible: Chocolate balls for only $2$ kr each!!! Bruno and Sofie immediately sta...
26,814
Chocolate Chip Fabrication Description: You are making a chocolate chip cookie using a machine that has a rectangular pan composed of unit squares. You have determined the shape of your cookie, which occupies some squares in that area. Each square of your cookie must be chocolate chipified. To make th...
26,815
Chocolate Division Description: Alf and Beata were two young adults living together a long, long time ago, before you could spend all your afternoons competing in programming. Their lives were thus much more boring than those of today’s young adults. How could you even survive back then, you might ask ...
26,816
Chocolates Description: “My mom always said life was like a box of chocolates. You never know what you’re gonna get." Forrest Gump is a young boy who goes to Greenbow County Central School. As a child, he enjoys running, dancing by swinging his hips, and eating chocolates. Most of all, he enjoys s...
26,817
Choosing Numbers Description: You regularly play a game with friends, and you’re tired of losing. The goal of the game is to end up with the largest number in your hand at the end. Initially there is a set of unique numbers on the table. At each turn, a player chooses a number from the table and puts i...
26,818
Chopping Trees Description: After many years of research, Lolle has finally disproved Lalexander’s conjecture (which stated that $(a+b)^2=a^2+b^2$). Now feeling done with his mathematical career, Lolle retreats to the forest. Once a week, he goes out to chop down trees for timber. Lolle chose to move t...
26,819
Chopping Wood Description: Given an unrooted tree structure as in the picture below, we chop it into pieces in the following way: pick the smallest numbered leaf, and remove the edge connecting that leaf to the tree. Then repeat this process until nothing is left of the tree. To record this process, w...
26,820
Christian's Piano Description: Christian wants to learn to play the piano but can only manage to play with his index finger right now. Currently, he is practicing hard to learn a piece. A piece is described by a sequence of keys to be pressed in order. For example, the piece abdaa indicates that he sho...
26,821
Christmas Gifts Description: At the Nordic Olympic Institute (NOI) the $S$ students have a tradition of exchanging gifts with their friends at christmas. More precisely, if $A$ and $B$ are friends either $A$ gives $B$ a gift or $B$ gives $A$ a gift. Last christmas there was a big scandal at NOI becaus...
26,822
Chromium Shipping Description: Greg Brandon Sr. is working at a shipping company in Redmond that specializes in shipping Chromium. Redmond contains $n$ intersections and $m$ two-way roads that directly connect two intersections (Redmond can be modelled as a graph with $n$ vertices and $m$ edges...
26,823
Chuck Description: You are given an matrix of $R$ rows and $C$ columns. All elements of the matrix have absolute value smaller than or equal to $10^4$. You may perform the following operations: Operation Notation Example Rotate $i$-th row of the matrix $k$ elements right ($1 \le...
26,824
Chugging Description: Alice and Bob have challenged each other to finish as many bottles as quickly as they can, an activity known as chugging in North American slang. It takes Alice $t_ A$ seconds to finish the first bottle. However, the bottle contents (gas, complex carbohydrates, alcohol) have ...
26,825
Cinema Crowds Description: The United Cinema Crowd Association of Stockholm plans to have a showing of Old computer scientists and their pieings at the local KTH Royal Institute of Technology cinema. Not until far too late did the auditor of the association point out that the board had booked far too ...
26,826
Cinema Crowds 2 Description: The United Cinema Crowd Association of Stockholm plans to have a showing of Old computer scientists and their pieings at the local KTH Royal Institute of Technology cinema. Not until far too late did the auditor of the association point out that the board had booked far to...
26,827
Cinema Seating Description: The United Cinema Crowd Association of Stockholm plans to have a showing of Old computer scientists and their pieings at the local KTH Royal Institute of Technology cinema. They have received bookings from $N$ computer scientists to attend the showing. The cinema itself is a...
26,828
Circle Description: One nice summer day while Mirko was drinking lemonade in his room... “Big brother!”, yells Stanko. “I wonder sometimes which of the two of us is the big one. What is it?”, Mirko asked. “Listen carefully! In the backyard I have $N$ pebbles arranged in a circle. Some of the pebbles are...
26,829
Circle Bounce Description: You are standing by the wall in a large, perfectly circular arena and you throw a tennis ball hard against some other part of the arena. After a given number of bounces, where does the tennis ball next strike the wall? Map the arena as a unit circle centered at the origin, with ...
26,830
Circle Passing Description: It is the first day of high school for Anouk; as a warm-up activity, her sports teacher is making the class play name-learning games. There are $2N$ students in the class. Most of them do not know each other, but there are $M$ pairs of best friends who do everything together...
26,831
Circle of Debt Description: The three friends Alice, Bob, and Cynthia always seem to get in situations where there are debts to be cleared among themselves. Of course, this is the “price” of hanging out a lot: it only takes a few resturant visits, movies, and drink rounds to get an unsettled balance. S...
26,832
Circle of Friends Description: There is a posse of friends sitting in a circle. Each friend is holding a card containing a positive integer. You would like to split the circle of friends into one or more groups. Each group must be a contiguous subsection of the circle. In addition, for each group, the bit...
26,833
Circuit Board Design Description: More specifically, each circuit design consists of a number of connection points with some connections between them such that the resulting graph is connected and does not have any cycles (i.e., the graph is a tree). You are free to place the connection points anywhere on...
26,834
Circuit Counting Description: Suppose you are given a sequence of $N$ integer-valued vectors in the plane $(x_ i,y_ i)$, $i = 1, \ldots , N$. Beginning at the origin, we can generate a path by regarding each vector as a displacement from the previous location. For instance, the vectors $(1,2)$, $(2...
26,835
Circuit Math Description: You are enrolled in the Computer Organization and Architecture course at your university. You decide to write a program to help check your work by computing the output value of a combinational digital circuit, given its inputs. Consider the circuit shown in Figure 1, which we use...
26,836
Circular Caramel Cookie Description: This year, your archrival Rob had the audacity to open up another factory for stroopwafels and they have already announced that their stroopwafels will be even bigger than yours. Although the exact size of the new stroopwafels is a well-kept secret, your industrial ...
26,837
Circular DNA Description: You have an internship with a bioinformatics research group studying DNA. A single strand of DNA consists of many genes, which fall into different categories called gene types. Gene types are delimited by specific nucleotide sequences known as gene markers. Each gene type ...
26,838
Circular Lock Description: For the fourth time this month only, the absent minded mathematics professor Bolkás had lost his keys. Realizing, that a change of personality to one that keeps track of trivialities seemed unlikely, he started to invent a lock with a non-material key. Of course, he could jus...
26,839
Circumsphere Description: You are given four points in space (i.e. $\mathbb {R}^3$). The points are not coplanar. In other words, there is no plane in space that contains all four points. It is guaranteed that under such assumption, there exists a (unique) sphere whose surface touches all four points. Fin...
26,840
Citadel Construction Description: The army wants to put up a new base in dangerous territory. The base will be surrounded by a citadel consisting of a number of straight walls. At every corner where two walls meet, there will be a watchtower. In order to enable efficient coordination in case of attack,...
26,841
Citations Description: Grace is going to read a certain scientific book. However, she is very careful about always reading the sources that books refer to, and also the sources of the sources, and so on. It usually ends up being the case that she reads quite a lot more books than just the one she origi...
26,842
Cities Description: In a far away kingdom, there are $N$ cities numbered between $0$ and $N - 1$. The cities are connected by $N - 1$ two-way roads. Each road has the same length, and connects exactly two cities, such that there is a unique path between any pair of cities. For any two cities $A$ ...
26,843
Citizenship Description: For this problem, assume that a calendar year has $12$ months of $365$ days, and each month has exactly the number of days below: month 01 02 03 04 05 06 07 08 09 10 11 12 days 31 28 31 30 31 30 31 31 30 31 30 31 For example, if you were to apply on 2024–...
26,844
City Bike Description: City bike is a popular commute method. But it is sometimes frustrating that some bike docking stations have few bikes, while others are almost full and have few empty docks. The bike company regularly sends trucks to relocate bikes to mitigate such issues. A truck is about to de...
26,845
City Destruction Description: Modan is playing a new action strategy game, where his goal is to destroy a city. A city is made up of $N$ buildings, where the $i$-th building initially has health $H_ i$. At every move, Modan can choose a building to attack, dealing $D$ damage to it. When a building’s h...
26,846
City Numbers Description: After the zombie invasion, everything in the country of Aabelrt was destroyed. To rebuild as quickly as possible, the government of Aabelrt decided to build the minimum possible number of roads between cities to make sure each city can reach every other city. Unfortunately, th...
26,847
City Park Description: Porto is blessed with a beautiful city park. The park, in the western section of the city, borders the Atlantic Ocean. It has great lawns, small forests, plenty of flowerbeds, a variety of ponds, and, in all, lots of points of interest. Porto families love the park and flock to i...
26,848
City Tour Description: During summer time, old cities in Europe are swarming with tourists who roam the streets and visit points of interest. Many old cities were built organically and not according to some architecture plan, but, strangely, their growth exhibits a similar pattern: the cities started from...
26,849
Class Field Trip Description: Instructors ann and ben firmly believe that everything should be alphabetical, especially names. (They also don’t believe in capital letters!) They take alphabetical order to such an extreme that they even order the letters of their names when listed together. For example,...
26,850
Class Picture Description: It’s time to take a class picture. As you know, this means all of the students have to line up in a row and smile for the camera. Of course, like any class, there are pairs of people who don’t like each other. These people refuse to stand beside each other for the picture. If...
26,851
Classical Counting Description: You have $N$ objects, each with $M$ copies. How many ways are there to take exactly $K$ of them? Two selections of size $K$ are considered different if the $K$-tuples for those selections are different. So, for example if $N=M=K=3$ (as in the second sample input), a...
26,852
Classrooms Description: The new semester is about to begin, and finding classrooms for orientation activities is always a headache. There are $k$ classrooms on campus and $n$ proposed activities that need to be assigned a venue. Every proposed activity has specfic starting time $s_ i$ and ending t...
26,853
Cleaning Pipes Description: All the pipes are at the same depth under ground. Therefore, whenever two pipes cross, they form an intersection. Luckily the pipe system was constructed in such a way that exactly two pipes meet at each such intersection. The wells do not count as intersections. Any number ...
26,854
Cleaning Robot Description: A company wishes to purchase a square-shaped cleaning robot to clean a rectangularly shaped room. Some parts of the room are obstructed. There are different robots of different sizes. Each robot can move horizontally and vertically in the room if no part of the robot inters...
26,855
Cliff Walk Description: One morning last summer, Charlotte was watching the moon and the sun and observed that the moon was full. As she lives along the Atlantic coast she knows that this means a larger variation in the tide compared to first and last quarter. With no rain in the air, it seemed like a ...
26,856
Climbing Description: Fiona is an expert climber. She often brings some pegs with her, which she nails in some strategic places in the rock wall, so that less experienced climbers can use them for support. Fiona can climb to anywhere in the wall, but hammering a peg needs some balance, so she can only ...
26,857
Climbing Stairs Description: Your workplace recently announced a staircase cup with some fabulous prizes to win. The rules of participation are simple: Each day, it is possible to gain one point, and at the end of the month, whoever has the most points wins. In order to get a point for a specific day, ...
26,858
Climbing Worm Description: A worm is at the bottom of a pole. It wants to reach the top, but it is too lazy to climb to the top without stopping. It can crawl up the pole a certain number of inches at a time, falling down a lesser number of inches right after while it rests. How many times does the wor...
26,859
Clinic Description: You work at a clinic. The clinic factors in the waiting time when selecting patients to treat next. This approach was adopted to prevent patients from having to wait too long before being treated. Your task is to help the clinic perform $3$ types of queries: * Process a patient arr...
26,860
Clock Breaking Description: After numerous unfortunate freak fatalities and the lawsuits, settlements, protests, and boycotts that naturally followed, the beleaguered executives at ACME Clock Manufacturers have decided they need to finally fix their disastrous quality control issues. It has been known ...
26,861
Clock Construction Description: Engineers at Spectre Imaging have decided to start investing in smart clock market. They are creating a prototype clock that will be able to show some images. The clock’s rectangular display consists of black-and-white pixels. A pixel can have two states: ON or OFF. Since i...
26,862
Clock Pictures Description: You have two pictures of an unusual kind of clock. The clock has $n$ hands, each having the same length and no kind of marking whatsoever. Also, the numbers on the clock are so faded that you can’t even tell anymore what direction is up in the picture. So the only thing ...
26,863
Closeness Queries Description: In an undirected graph, we define the distance between two vertices $u$ and $v$ as the minimum length of a sequence of edges starting at $u$ and ending at $v$. Given $Q$ pairs of vertices in the graph, can you for each pair of vertices compute the distance between the...
26,864
Closest Pair Description: ## Input Input contains several test cases. Each test case begins with an integer $n$ ($2 \le n \le 100\, 000$). Then follows a list of $n$ points, one per line, each of the form $x$ $y$. Coordinates are floating point values with at most $2$ decimals and absolute value ...
26,865
Closest Pair (Uniform) Description: ## Input Input contains several test cases. Each test case begins with an integer $n$ ($2 \le n \le 100\, 000$). Then follows a list of $n$ points, one per line, each of the form $x$ $y$. Coordinates are floating point values with at most $2$ decimals and absolu...
26,866
Closest Sums Description: Given is a set of integers and then a sequence of queries. A query gives you a number and asks to find a sum of two distinct numbers from the set which is closest to the query number. ## Input Input contains multiple cases. Each case starts with an integer $1 < n \le 1000$. ...
26,867
Closing the Borders Description: After an epidemic hit most of Europe, countries have started announcing closures of their borders for travel. This is a problem for you, since you are currently on vacation in France, far away from your home in Sweden. You hope to get home before enough borders close so...
26,868
Closing the Loop Description: Given a bag full of rope segments, you will build the longest loop of rope while alternating colors. The bag contains $S$ segments and each segment will either be blue ($B$) or red ($R$). You are required to alternate between colors and because of this requirement you migh...
26,869
Clumsy Cardinals Description: Everyone knows that in the game chess, a bishop moves diagonally. Boring! Consider a new piece called a cardinal. A cardinal moves diagonally, like a bishop but they are clumsy. If its movement brings a cardinal adjacent to another piece, it trips and falls on the othe...
26,870
Coast Length Description: The island municipality of Soteholm is required to write a plan of action for their work with emission of greenhouse gases. They realize that a natural first step is to decide whether they are for or against global warming. For this purpose they have read the IPCC report on cl...
26,871
Cobweb Description: You are given $n$ cards, the $i$-th of which has a character $c_ i$ written on it. You want to arrange some or all of these cards so that they form a sequence. However, you cannot arrange them arbitrarily, as you are also given $n - 1$ rules in the form of $(i, j)$, meaning ...
26,872
Coci Description: The 3rd round of COCI is already here! In order to bet on predict the scores, we have assumed the following: * If contestant $A$ scored strictly more points than contestant $B$ in each of the first two rounds, then in the third round $A$ will score at least an equal amoun...
26,873
Cocoa Coalition Description: Alice and Bob decide to share a chocolate bar, which is an $n$ by $m$ rectangular grid of chocolate cells. They decide that Alice should get $a < n \cdot m$ pieces and that Bob should get $b = n \cdot m - a$ pieces. To split the chocolate bar, they repeatedly take a sin...
26,874
Coconut Splat Description: Coconut Splat is one of Theta’s favorite counting-out games. It goes like this: initially, all players stand in a circle with their hands folded together (like an intact coconut). In clockwise order, one player touches the hands of the other players and says the rhyme: “Co-co...
26,875
Code Cleanups Description: Rather than investing a lot of time figuring out why this degradation in productivity occurred, the line manager suggests that they loosen their requirement: developers can push code that weakly violates the guidelines as long as they run cleanup phases on the code from time ...
26,876
Code Guessing Description: Bob tells Alice the positions of her two cards. The goal of Alice is to guess the digits on Bob’s two cards. Can Alice uniquely determine these two digits and guess them correctly? ## Input The input has two integers $p, q$ ($1 \leq p < q \leq 9$) on the first line, giv...
26,877
Code Names Description: You are given $W$, a set of $N$ words that are anagrams of each other. There are no duplicate letters in any word. A set of words $S \subseteq W$ is called “swap-free” if there is no way to turn a word $x \in S$ into another word $y \in S$ by swapping only a single p...
26,878
Code Permutations Description: You are soon to graduate from the mathemagician school of Hagworts, and you’re quite content with yourself; all the hard work and elbowing has finally paid off. Being successful at most of your endeavors you would normally end up a herald of sound reasoning and good mathe...
26,879
Code Theft Description: The screening would work as follows: Every time new code was checked in, the full contents of the changed files where matched against a repository of known open source code. For each file the longest match, in number of consecutive lines, should be reported. Comparison is done ...
26,880
Code to Save Lives Description: Daenerys and her fellow friends decided to go on a magical adventure to find the mystical scientist to cure her village of disease. On her adventure she faces the winter and desert until she finally found the genius scientist, and while Daenerys explained her dire situat...
26,881
Codenames Description: Codenames is a popular board game. Two teams compete by each having a “spymaster” give one-word clues that can point to multiple words on the board. The other players on the team attempt to guess their team’s words while avoiding the words of the other team. The objective is to b...
26,882
Codes Description: Error correcting codes are used in a wide variety of applications ranging from satellite communication to music CDs. The idea is to encode a binary string of length $k$ as a binary string of length $n>k$, called a codeword, in such a way that even if some bit(s) of the encoding a...
26,883
Codforces Description: Nicolas wants to start a competitive fishing career in the codforces™ championships. There are a lot of different divisions to compete in, but since Nicolas is a new participant in codforces™ he must start in the lowest division (division 1). Nicolas goal is to as quickly as poss...
26,884
Coffee Cup Combo Description: Jonna is a university student who attends $n$ lectures every day. Since most lectures are way too simple for an algorithmic expert such as Jonna, she can only stay awake during a lecture if she is drinking coffee. During a single lecture she needs to drink exactly one cup ...
26,885
Coffee Date Description: Erika and Leah have not had a cup of coffee together for too long, and want to meet up today. Both of them like all the coffee shops in the city, so they decide to meet up at the coffee shop where they can see each other as soon as possible. As they both live right by bus stop...
26,886
Coin Counter Description: Given an image of a set of Swedish coins valued 1, 5 and 10 SEK, what is their sum? The coins look like this: ## Input The input is a JPEG-formatted image with dimensions $1000 \times 1000$. No coin will be covered by other coins such that the visible parts of it is divided in...
26,887
Coin Stacks Description: The players win the game if they manage to remove all the coins. Is it possible for them to win the game, and if it is, how should they play? ## Input The first line of input contains an integer $n$ ($2 \le n \le 50$), the number of coin stacks. Then follows a line containing...
26,888
Cokolada Description: A new type of chocolate arrived in the local shop. The chocolate comes in bars, each bar consisting of $N$ squares. Bars are factory made and only come in sizes which are full powers of two. In other words a single bar has $1, 2, 4, 8, 16, \dots $ squares. To fully asses the qual...
26,889
Cold-puter Science Description: We’re not going to sugar-coat it: Chicago’s winters can be rough. The temperatures sometimes dip to uncomfortable levels and, after last year’s “polar vortex”, the University of Chicago Weather Service wants to find out exactly how bad the winter was. More specifically, ...
26,890
Collapse Description: We model the situation as follows. Each island has a threshold $T_ i$ on the amount of incoming goods (for simplicity we assume that there is only a single commodity of goods) it needs to receive per lunar cycle in order for the society of the island to sustain itself. If the ...
26,891
Collatz Conjecture Description: The Collatz Conjecture is an interesting phenomenon. Though its principle is very simple, it still remains among unresolved problems in mathematics, even after many years of study. However, the years of intensive research brought at least some results, which is a huge ad...
26,892
Collatz Conjecture Description: About a century later Lothar Collatz applied this function to the sequence $1, 1, 1, \dots , 1$, and observed that $f$ always equalled $1$. Based on this, he conjectured that $f$ is always a constant function, no matter what the sequence $a_ i$ is. This conjecture, now w...
26,893
Collecting Beepers Description: Karel is a robot who lives in a rectangular coordinate system where each place is designated by a set of integer coordinates ($x$ and $y$). Your job is to design a program that will help Karel pick up a number of beepers that are placed in her world. To do so you mus...
26,894
Colliding Traffic Description: For a boat on a small, constrained body of water, other traffic can be a major hazard. The more traffic there is in the same area, the higher the risk of a collision. Your job is to monitor traffic and help detect likely collisions before they occur. You have sensors to dete...
26,895
Collusion on Two Wheels Description: Two bicycle courier services have been competing in Metro City for many years, stealing customers back and forth from one another. Recently, they have come to realize that they would be better off if they could attract new customers instead. A problem is that, over ...
26,896
Color Codes Description: While Gray codes are great, they are also a bit, well... gray1. In this problem, we look at a much more colorful variant. For an integer $n \ge 1$ and set of integers $P \subseteq \{ 1, \ldots , n\} $, we say that an ordering $(x_1, \ldots , x_{2^ n})$ of all $n$-bit b...
26,897
Color Tubes Description: There is a new puzzle generating buzz on social media—Color Tubes. The rules are relatively simple: you are given $n+1$ tubes filled with $3n$ colored balls. Each tube can hold at most 3 balls, and each color appears on exactly 3 balls (so there are $n$ colors). Using a se...
26,898
Color Walk Description: Alice and Bob are playing a game on a directed graph, fully visible to both of them. The graph has $n$ nodes labelled $1$ through $n$ and directed arcs between nodes. Each arc is colored either red or black. In addition to the graph, there is a queue of capacity $k$, fully visible t...
26,899