Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,880 problems

High Card Wins
Medium4
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Angry Cows (Silver)
Medium4
Binary search, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Subsequences Summing to Sevens
Medium4
Prefix sum, Hash map
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Collecting Stamps 2
Medium4
Prefix sum, Combinatorics
No attempts yet
Time limit
2s
Memory limit
256 MB
Judgeable
Milk Pails
Medium4
BFS, Simulation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Stock Purchase Plan
Medium4
Dynamic programming, Binary search
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Longest Increasing Subsequence 2
Medium4
Binary search, Dynamic programming
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Mileage Course Registration
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
ABC Street
Medium4
Dynamic programming
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sums of Sums (Small)
Medium4
Sorting, Prefix sum
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Dynamic Grid (Large)
Medium4
BFS, Matrix+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
gCampus (Small)
Medium4
Shortest path, Graph
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Cyclic Rotations
Medium4
String matching
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Telephones
Medium4
Greedy, Array
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Consecutive Sums
Medium4
Math, Number theory
No attempts yet
Time limit
1s
Memory limit
64 MB
Judgeable
Pretty Good Proportion (Small)
Medium4
Brute force, Prefix sum
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
English and French (Small)
Medium4
Brute force, Bit manipulation+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Noisy Neighbors
Medium4
Brute force, Bit manipulation
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Mushroom Monster (Large)
Medium4
Greedy, Simulation+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Cube IV (Small)
Medium4
DFS, Dynamic programming+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minesweeper Minimum Clicks
Medium4
BFS, Graph+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minimum Clicks in Minesweeper
Medium4
DFS, Graph+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Packing Files onto Discs
Medium4
Greedy, Two pointers+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Data Packing
Medium4
Greedy, Two pointers+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Cookie Farms
Medium4
Greedy, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Rational Number Tree (Small)
Medium4
Tree, BFS+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Manage your Energy (Small)
Medium4
Dynamic programming
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Lawnmower (Small)
Medium4
Greedy, Matrix
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Lawnmower (Large)
Medium4
Greedy, Matrix
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Decomposition Sum 2
Medium4
Brute force, Math
No attempts yet
Time limit
0.25s
Memory limit
512 MB
Judgeable
Ocean View
Medium4
Dynamic programming
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Diamond Inheritance (Small)
Medium4
Graph, DFS
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Dancing With the Googlers (Large)
Medium4
Greedy
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Recycled Numbers (Small)
Medium4
Brute force, String
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Quake Live Team Split
Medium4
Dynamic programming, Brute force
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Meeting Point (Small)
Medium4
Shortest path, Graph
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Number Sets (Small)
Medium4
Union-find, Number theory
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Irregular Expressions (Small)
Medium4
Brute force, String
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Twibet (Large)
Medium4
Graph, DFS
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Closing the Loop (Small)
Medium4
Greedy, Sorting
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Snapper Chain
Medium4
Bit manipulation, Math
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Odd Man Out
Medium4
Bit manipulation, Hash map
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Wi-Fi Towers (Small)
Medium4
Graph, Brute force+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Decision Tree
Medium4
Tree, Recursion+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Watersheds (Small)
Medium4
Graph, DFS+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Welcome to Code Jam (Small)
Medium4
Dynamic programming, String
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Painting a fence (small)
Medium4
Brute force, Intervals+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minimum Keypresses for Text Entry
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Counting Ugly Expressions
Medium4
Brute force, Recursion+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minimum Scalar Product (Small)
Medium4
Sorting, Greedy+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Minimum Scalar Product (Large)
Medium4
Sorting, Greedy+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Milkshakes (Large)
Medium4
Greedy, Implementation
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Train Timetable (Small)
Medium4
Greedy, Sorting+2
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
Sleep Disorder
Medium4
Math, Implementation
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Ceiling Function
Medium4
Tree, Implementation+1
No attempts yet
Time limit
5s
Memory limit
512 MB
Judgeable
PIZZA ALVOLOC
Medium4
Geometry
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Bit Friendship Index
Medium4
String, Greedy+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Weekly Meeting
Medium4
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Household Ledger
Medium4
Prefix sum
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Climbing to the Information Science Building
Medium4
Prefix sum, Array+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Infinite string
Medium4
String, String matching
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
DNA Password
Medium4
Sliding window, String+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
The Enemy of My Enemy
Medium4
Graph, BFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Scrooge Minho
Medium4
Tree, Graph+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Liars
Medium4
Brute force, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Restaurant for Bears
Medium4
Implementation, Greedy+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
ABC
Medium4
Greedy, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
AB String
Medium4
Greedy, Combinatorics+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Number Game
Medium4
Number theory, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Wolves and Proper Words
Medium4
Stack, Greedy
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Important Test
Medium4
Array, Prefix sum+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rational Sequence
Medium4
Math, Number theory+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
North North West
Medium4
Math, String+2
No attempts yet
Time limit
8s
Memory limit
512 MB
Judgeable
Do Not Touch Anything
Medium4
Math, Greedy
No attempts yet
Time limit
1s
Memory limit
32 MB
Judgeable
Nailro Rail Pass Trip
Medium4
Shortest path, Graph
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Fast Exponentiation
Medium4
Math, Bit manipulation+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Combinations
Medium4
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Harps and Tails
Medium4
Hash map, Greedy+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Tree
Medium4
Graph, Union-find+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Drawing Pebbles
Medium4
Combinatorics, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Stacking Blocks
Medium4
Greedy, Matrix+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Roman numeral conversion
Medium4
String, Implementation+2
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Q-index
Medium4
Sorting, Array
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Game Rank
Medium4
Simulation, Implementation
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Dolphin
Medium4
Math, Binary search+1
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Rearrange
Medium4
Greedy, Sorting
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Far Far Away
Medium4
Tree, DFS+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Rearranging a Sequence
Medium4
Linked list, Implementation+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Justice Rains from Above!
Medium4
Sorting, Math+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Card String
Medium4
Greedy, String+2
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Evenly Spaced Triples
Medium4
Hash map, Array
No attempts yet
Time limit
1s
Memory limit
256 MB
Judgeable
Secret Meeting
Medium4
Shortest path, Graph+1
No attempts yet
Time limit
1s
Memory limit
128 MB
Judgeable
Battle Simulation
Medium4
Stack, String+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Sticky Situation
Medium4
Sorting, Greedy
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Fridge Magnets
Medium4
Greedy, Math+2
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
A Series of Tubes
Medium4
Graph, DFS
No attempts yet
Time limit
1s
Memory limit
512 MB
Judgeable
Stick Game
Medium4
Greedy, Sorting
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Counting Equilateral Triangles
Medium4
Prefix sum, Math+1
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Minimum energy × delay product
Medium4
Dynamic programming, Implementation
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable
Elevator
Medium4
Geometry, Math
No attempts yet
Time limit
2s
Memory limit
512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
High Card WinsAssign each of Bessie's N cards to a round against Elsie's fixed play order to win the most rounds with the higher card.	Medium4	GreedySorting	No attempts yet	2s	512 MB	Judgeable
Angry Cows (Silver)Find the smallest integer blast radius R so K intervals of length 2R cover all N hay bale positions on a line.	Medium4	Binary searchGreedy+1	No attempts yet	2s	512 MB	Judgeable
Subsequences Summing to SevensFind the length of the longest contiguous group of cows whose IDs sum to a multiple of 7.	Medium4	Prefix sumHash map	No attempts yet	2s	512 MB	Judgeable
Collecting Stamps 2Insert one J, O, or I stamp at any position to maximize the number of triples that read J, O, I in order.	Medium4	Prefix sumCombinatorics	No attempts yet	2s	256 MB	Judgeable
Milk PailsFill, empty, and pour two pails of sizes X and Y within K moves to get a combined amount as close to M as possible.	Medium4	BFSSimulation	No attempts yet	2s	512 MB	Judgeable
Stock Purchase PlanFor each test case, decide whether the daily prices contain a strictly increasing subsequence of length K.	Medium4	Dynamic programmingBinary search	No attempts yet	5s	512 MB	Judgeable
Longest Increasing Subsequence 2Given up to 1,000,000 numbers, compute the length of the longest strictly increasing subsequence.	Medium4	Binary searchDynamic programming	No attempts yet	1s	512 MB	Judgeable
Mileage Course RegistrationGiven each course rival bids and capacity, bid 1 to 36 points per chosen course, winning ties, to take the most courses with m points.	Medium4	GreedySorting	No attempts yet	1s	128 MB	Judgeable
ABC StreetStarting from block 1, hop forward across A, B, C blocks in repeating order to reach block N while minimizing the sum of squared jump lengths.	Medium4	Dynamic programming	No attempts yet	2s	512 MB	Judgeable
Sums of Sums (Small)You sort every contiguous subarray sum of an array and answer range sums over the sorted list.	Medium4	SortingPrefix sum	No attempts yet	5s	512 MB	Judgeable
Dynamic Grid (Large)Point updates flip binary grid cells and each query asks for the number of edge-connected groups of 1s.	Medium4	BFSMatrix+1	No attempts yet	5s	512 MB	Judgeable
gCampus (Small)For each road, decide whether it lies on a shortest path between some pair of offices and list the ones that never do.	Medium4	Shortest pathGraph	No attempts yet	5s	512 MB	Judgeable
Cyclic RotationsCount the left rotations of binary string B that exactly equal binary string A.	Medium4	String matching	No attempts yet	2s	512 MB	Judgeable
TelephonesAdd the fewest phones to empty desks so a ring hops from the first desk to the last with each hop spanning at most D.	Medium4	GreedyArray	No attempts yet	1s	64 MB	Judgeable
Consecutive SumsPrint every run of two or more consecutive positive integers that sums to N, ordered by starting value.	Medium4	MathNumber theory	No attempts yet	1s	64 MB	Judgeable
Pretty Good Proportion (Small)Given a binary string and a target fraction F, find the start index of the contiguous substring whose share of 1s is closest to F.	Medium4	Brute forcePrefix sum	No attempts yet	5s	512 MB	Judgeable
English and French (Small)Assign each unknown sentence to English or French so the number of words appearing in both languages is as small as possible.	Medium4	Brute forceBit manipulation+1	No attempts yet	5s	512 MB	Judgeable
Noisy NeighborsPlace N tenants on an R by C grid to minimize the number of shared walls between occupied neighbors.	Medium4	Brute forceBit manipulation	No attempts yet	5s	512 MB	Judgeable
Mushroom Monster (Large)From plate counts taken every 10 seconds, compute the minimum mushrooms eaten under free eating and under the smallest consistent constant rate.	Medium4	GreedySimulation+1	No attempts yet	5s	512 MB	Judgeable
Cube IV (Small)Given a square grid holding 1 to S squared, find the smallest start of the longest chain that steps to an orthogonal neighbor one higher and report its length.	Medium4	DFSDynamic programming+1	No attempts yet	5s	512 MB	Judgeable
Minesweeper Minimum ClicksCount the minimum clicks to reveal all safe cells, where each zero region opens with one click and each leftover numbered cell needs its own.	Medium4	BFSGraph+1	No attempts yet	5s	512 MB	Judgeable
Minimum Clicks in MinesweeperFind the fewest clicks that reveal every safe cell, since one click opens each zero region and each remaining safe cell costs one click.	Medium4	DFSGraph+1	No attempts yet	5s	512 MB	Judgeable
Packing Files onto DiscsPack all files onto the fewest discs of capacity X with at most two files per disc.	Medium4	GreedyTwo pointers+1	No attempts yet	5s	512 MB	Judgeable
Data PackingPack files onto discs holding at most two files of total size X using the fewest discs.	Medium4	GreedyTwo pointers+1	No attempts yet	5s	512 MB	Judgeable
Cookie FarmsDecide how many cookie farms to buy before waiting so the time to hold X cookies is as short as possible.	Medium4	GreedyMath	No attempts yet	5s	512 MB	Judgeable
Rational Number Tree (Small)Given the level-order listing of the rational number tree, find the n-th fraction and the position of a given fraction.	Medium4	TreeBFS+1	No attempts yet	5s	512 MB	Judgeable
Manage your Energy (Small)Allocate limited energy across ordered activities, regaining R after each up to cap E, to maximize value times energy spent.	Medium4	Dynamic programming	No attempts yet	5s	512 MB	Judgeable
Lawnmower (Small)Decide if row and column cuts of a mower that only lowers grass can produce the given target heights from a uniform lawn.	Medium4	GreedyMatrix	No attempts yet	5s	512 MB	Judgeable
Lawnmower (Large)Decide whether a target grid of grass heights is reachable from height 100 by cutting whole rows or columns down to chosen levels.	Medium4	GreedyMatrix	No attempts yet	5s	512 MB	Judgeable
Decomposition Sum 2Find the smallest M with M plus its digit sum equal to N, or print 0 when no such M exists.	Medium4	Brute forceMath	No attempts yet	0.25s	512 MB	Judgeable
Ocean ViewDestroy as few houses as possible so the heights of the houses left standing grow strictly from the lake eastward.	Medium4	Dynamic programming	No attempts yet	5s	512 MB	Judgeable
Diamond Inheritance (Small)Decide whether any pair of classes in each inheritance diagram has two distinct inheritance paths between them.	Medium4	GraphDFS	No attempts yet	5s	512 MB	Judgeable
Dancing With the Googlers (Large)Given each dancer's total of three close scores and a limit on surprising splits, count the most dancers that reach a best score of p.	Medium4	Greedy	No attempts yet	5s	512 MB	Judgeable
Recycled Numbers (Small)Count pairs (n, m) in [A, B] with equal digits where m is a rotation of n with no leading zero.	Medium4	Brute forceString	No attempts yet	5s	512 MB	Judgeable
Quake Live Team SplitSplit an even number of players with given skill levels into two equal-size teams so the team totals differ as little as possible.	Medium4	Dynamic programmingBrute force	No attempts yet	5s	512 MB	Judgeable
Meeting Point (Small)Friends with different speeds start from given cities and must meet in one city, so minimize the worst arrival time over all cities.	Medium4	Shortest pathGraph	No attempts yet	5s	512 MB	Judgeable
Number Sets (Small)Count how many disjoint sets remain after merging numbers in [A, B] that share a prime factor of at least P.	Medium4	Union-findNumber theory	No attempts yet	5s	512 MB	Judgeable
Irregular Expressions (Small)Decide if any substring of each short lowercase string splits into matching outer words with two or more vowels around a middle word with at least one vowel.	Medium4	Brute forceString	No attempts yet	5s	512 MB	Judgeable
Twibet (Large)In a graph where each monk follows exactly one other, count for every starter how many monks hear the whisper passed down through followers.	Medium4	GraphDFS	No attempts yet	5s	512 MB	Judgeable
Closing the Loop (Small)Pick equal numbers of red and blue segments with the largest lengths and subtract one centimeter per knot to get the longest alternating loop.	Medium4	GreedySorting	No attempts yet	5s	512 MB	Judgeable
Snapper ChainGiven N chained snappers acting as a binary counter and K snaps, decide whether the lamp on the last snapper receives power.	Medium4	Bit manipulationMath	No attempts yet	5s	512 MB	Judgeable
Odd Man OutGiven an odd-length list where every number appears twice except one, find the number that appears once.	Medium4	Bit manipulationHash map	No attempts yet	5s	512 MB	Judgeable
Wi-Fi Towers (Small)Choose which towers to upgrade to protocol B so the total score is maximized, where upgrading a tower forces every tower in its range to be upgraded too.	Medium4	GraphBrute force+1	No attempts yet	5s	512 MB	Judgeable
Decision TreeParse a recursively defined decision tree, then for each animal walk the tree using its features and multiply node weights to get the probability.	Medium4	TreeRecursion+2	No attempts yet	5s	512 MB	Judgeable
Watersheds (Small)Given a height grid, follow each cell's outflow to its sink and label cells by shared sink, choosing basin letters to make the row-wise string smallest.	Medium4	GraphDFS+2	No attempts yet	5s	512 MB	Judgeable
Welcome to Code Jam (Small)Count how many ways the 19-character phrase "welcome to code jam" appears as a subsequence of the input line, and print the last four digits.	Medium4	Dynamic programmingString	No attempts yet	5s	512 MB	Judgeable
Painting a fence (small)From up to 10 offers, choose the fewest that cover sections 1 to 10000 using at most 3 distinct colors.	Medium4	Brute forceIntervals+1	No attempts yet	5s	512 MB	Judgeable
Minimum Keypresses for Text EntryAssign each letter to a key and a position so that total presses, the frequency times the position, is minimized.	Medium4	GreedySorting+2	No attempts yet	5s	512 MB	Judgeable
Counting Ugly ExpressionsInsert +, -, or nothing between adjacent digits of a digit string, count how many of the 3^(D-1) expressions evaluate to a number divisible by 2, 3, 5, or 7.	Medium4	Brute forceRecursion+2	No attempts yet	5s	512 MB	Judgeable
Minimum Scalar Product (Small)Permute two vectors to minimize their dot product and print the minimum.	Medium4	SortingGreedy+1	No attempts yet	5s	512 MB	Judgeable
Minimum Scalar Product (Large)Reorder the coordinates of two equal-length integer vectors so their scalar product is as small as possible, and report that minimum for each test case.	Medium4	SortingGreedy+2	No attempts yet	5s	512 MB	Judgeable
Milkshakes (Large)Assign each of N flavors malted or unmalted so every customer gets a liked type, using the fewest malted batches, or report IMPOSSIBLE.	Medium4	GreedyImplementation	No attempts yet	5s	512 MB	Judgeable
Train Timetable (Small)Given a day's timetable and a turnaround time, find the minimum number of trains that must start the day parked at each of the two stations.	Medium4	GreedySorting+2	No attempts yet	5s	512 MB	Judgeable
Sleep DisorderConcatenate the natural numbers 1, 2, 3, ... into one digit string and return the digit at position N.	Medium4	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Ceiling FunctionInsert each prototype's values into a binary search tree in order, then count how many distinct tree shapes appear across the prototypes.	Medium4	TreeImplementation+1	No attempts yet	5s	512 MB	Judgeable
PIZZA ALVOLOCGiven four points on the boundary of a convex polygon in the order picked, decide whether segments (1,2) and (3,4) split the pizza into four pieces.	Medium4	Geometry	No attempts yet	1s	128 MB	Judgeable
Bit Friendship IndexGiven two equal-length binary strings, find the minimum number of digit changes and character swaps to make them identical.	Medium4	StringGreedy+1	No attempts yet	1s	128 MB	Judgeable
Weekly MeetingFor each member's house, add the shortest distances to two fixed nodes and sum all results, counting unreachable as -1.	Medium4	Shortest pathGraph+1	No attempts yet	1s	512 MB	Judgeable
Household LedgerProcess point additions and range-sum queries on a ledger of N days.	Medium4	Prefix sum	No attempts yet	1s	512 MB	Judgeable
Climbing to the Information Science BuildingFind the crossing point k minimizing left-road distance from 1 to k plus crosswalk k plus right-road distance from k to n; output the smallest such k and the minimum distance.	Medium4	Prefix sumArray+2	No attempts yet	2s	512 MB	Judgeable
Infinite stringGiven two strings of length at most 50, decide whether each repeated infinitely produces the same infinite string.	Medium4	StringString matching	No attempts yet	2s	512 MB	Judgeable
DNA PasswordCount the length-\|P\| substrings of a DNA string that contain at least the required number of each of A, C, G, and T.	Medium4	Sliding windowString+2	No attempts yet	2s	512 MB	Judgeable
The Enemy of My EnemyDecide whether the N people can be split into two camps so that every given hostile pair lands on opposite sides, which is exactly bipartiteness.	Medium4	GraphBFS+2	No attempts yet	2s	512 MB	Judgeable
Scrooge MinhoGiven a tree, place one fire station at the vertex minimizing the maximum distance to any other vertex, and output that distance.	Medium4	TreeGraph+2	No attempts yet	2s	512 MB	Judgeable
LiarsGiven a circular string of answers about whether the right neighbor is a liar, find the minimum number of liars consistent with all answers, or -1.	Medium4	Brute forceImplementation+1	No attempts yet	2s	512 MB	Judgeable
A Restaurant for BearsEach arriving bear takes the smallest empty chair at or above its wanted number that is at least d away from every seated bear.	Medium4	ImplementationGreedy+1	No attempts yet	2s	512 MB	Judgeable
ABCFind the lexicographically smallest length-N string over A, B, C that has exactly K pairs i < j with S[i] < S[j].	Medium4	GreedyCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
AB StringFind the length-N A/B string whose number of (A before B) pairs equals K, choosing the lexicographically smallest such string.	Medium4	GreedyCombinatorics+1	No attempts yet	2s	512 MB	Judgeable
Number GameFind the smallest positive N under 1e9 satisfying N mod P1 = X1, N mod P2 = X2, N mod P3 = X3, else print -1.	Medium4	Number theoryMath+2	No attempts yet	2s	512 MB	Judgeable
Wolves and Proper WordsGiven a word of w, o, l, f, decide whether it is a concatenation of blocks w^n o^n l^n f^n for n >= 1.	Medium4	StackGreedy	No attempts yet	2s	512 MB	Judgeable
Important TestFor each variant, find the longest prefix solvable in t minutes given he may replace at most one task time with t0. Since order is fixed, choose the single task in that prefix whose copying saves the most time.	Medium4	ArrayPrefix sum+1	No attempts yet	2s	512 MB	Judgeable
Rational SequenceGiven p/q, find its index in the breadth-first ordering of the Calkin-Wilf tree, where each node p/q has children p/(p+q) and (p+q)/q.	Medium4	MathNumber theory+2	No attempts yet	2s	512 MB	Judgeable
North North WestA direction string is built from copies of north and west; each prefix copy shifts the angle by 90/2^n, so compute the resulting angle as an integer or reduced fraction.	Medium4	MathString+2	No attempts yet	8s	512 MB	Judgeable
Do Not Touch AnythingGiven an R by C grid and an N by N square, find the fewest squares needed to cover the whole grid, allowing overhang and overlap.	Medium4	MathGreedy	No attempts yet	1s	32 MB	Judgeable
Nailro Rail Pass TripCompare the cheapest itinerary cost with and without a rail pass that discounts some fares, and decide if the pass is worth it.	Medium4	Shortest pathGraph	No attempts yet	1s	512 MB	Judgeable
Fast ExponentiationCompute A raised to the power X modulo 1,000,000,007, where A and X can be up to 10^18.	Medium4	MathBit manipulation+1	No attempts yet	1s	512 MB	Judgeable
CombinationsGiven up to 1000 pairs (n, k), compute the binomial coefficient C(n, k) modulo 10^9+7 for each pair.	Medium4	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Harps and TailsFlip any subset of columns of an H/T grid; find the maximum number of rows that can be made all-H.	Medium4	Hash mapGreedy+2	No attempts yet	2s	512 MB	Judgeable
TreeGiven up to 10 graphs, decide for each whether it is a tree, allowing self-loops and duplicate edges.	Medium4	GraphUnion-find+1	No attempts yet	2s	512 MB	Judgeable
Drawing PebblesGiven pebble counts per color, compute the probability that K randomly drawn distinct pebbles all share one color, printed to 10 decimals.	Medium4	CombinatoricsMath+2	No attempts yet	2s	512 MB	Judgeable
Stacking BlocksGiven a 0/1 top view plus front and side height maxima, output the tallest cube stack arrangement matching all three views, or -1.	Medium4	GreedyMatrix+1	No attempts yet	1s	128 MB	Judgeable
Roman numeral conversionFor each of T inputs, convert a Roman numeral to its value in Arabic numerals or an Arabic numeral between 1 and 3999 to its Roman form.	Medium4	StringImplementation+2	No attempts yet	1s	128 MB	Judgeable
Q-indexGiven n citation counts, find the largest k such that at least k papers have k or more citations and the rest have at most k.	Medium4	SortingArray	No attempts yet	1s	512 MB	Judgeable
Game RankGiven a string of wins and losses, simulate the star-based ranking system and report the final rank or Legend.	Medium4	SimulationImplementation	No attempts yet	1s	512 MB	Judgeable
DolphinGiven a position n, print the n-th phrase in the repeating block-based dolphin sequence.	Medium4	MathBinary search+1	No attempts yet	1s	512 MB	Judgeable
RearrangeChoose an ordering of the array, subtract elements from n in that order until n drops to 0 or below, and report the smallest achievable result.	Medium4	GreedySorting	No attempts yet	1s	512 MB	Judgeable
Far Far AwayGiven a directed tree rooted at city 1 with weighted edges, find the maximum root-to-node path weight, or -1 if it stays below M.	Medium4	TreeDFS+2	No attempts yet	2s	512 MB	Judgeable
Rearranging a SequenceGiven the sequence 1 to n, each request moves a named integer to the front while keeping the rest in order; output the final sequence.	Medium4	Linked listImplementation+1	No attempts yet	2s	512 MB	Judgeable
Justice Rains from Above!Given each robot's coordinates and missile speed, output the robot indices sorted by hit time (distance divided by speed), breaking ties by smaller index.	Medium4	SortingMath+1	No attempts yet	1s	128 MB	Judgeable
Card StringGiven uppercase letters taken left to right, each new card is placed at the front or back of the growing string; find the lexicographically smallest result.	Medium4	GreedyString+2	No attempts yet	1s	256 MB	Judgeable
Evenly Spaced TriplesGiven N distinct positions on a line, count how many triples of points have the middle point exactly halfway between the other two.	Medium4	Hash mapArray	No attempts yet	1s	256 MB	Judgeable
Secret MeetingGiven a weighted undirected graph and K friends' rooms, pick the room minimizing the sum of shortest-path distances from all friends; break ties by smallest room.	Medium4	Shortest pathGraph+1	No attempts yet	1s	128 MB	Judgeable
Battle SimulationRead a monster attack string and output the mech's counters, merging each earliest triple of R, B, L into one C.	Medium4	StackString+1	No attempts yet	2s	512 MB	Judgeable
Sticky SituationGiven N stick lengths, decide whether some three of them can form a triangle with positive area.	Medium4	SortingGreedy	No attempts yet	2s	512 MB	Judgeable
Fridge MagnetsGiven a multiset of digit magnets, find the smallest positive integer that cannot be assembled from them, where the answer can exceed 64-bit range.	Medium4	GreedyMath+2	No attempts yet	2s	512 MB	Judgeable
A Series of TubesGiven a connected undirected graph, decide whether its edges can be oriented so that the result stays strongly connected.	Medium4	GraphDFS	No attempts yet	1s	512 MB	Judgeable
Stick GameGiven counts of sticks of distinct lengths, find the maximum number of rectangles (squares allowed) that can be built using each stick at most once.	Medium4	GreedySorting	No attempts yet	2s	512 MB	Judgeable
Counting Equilateral TrianglesGiven arc lengths around a circle and points at the boundaries, count equilateral triangles whose three vertices are among the points.	Medium4	Prefix sumMath+1	No attempts yet	2s	512 MB	Judgeable
Minimum energy × delay productChoose a frequency level for each of P programs in order to minimize the total energy times delay product, including a fixed cost per frequency change.	Medium4	Dynamic programmingImplementation	No attempts yet	2s	512 MB	Judgeable
ElevatorGiven a rectangle and two circles, decide whether both circles fit inside the rectangle without overlapping.	Medium4	GeometryMath	No attempts yet	2s	512 MB	Judgeable