Interview warm-up

Short whiteboard warmups

Under construction

Still being built. Things may change

Total results4,731 problems

ResistanceEasy1
Hash map, ImplementationNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Escape from a RectangleEasy1
Math, Geometry +1No attempts yetTime limit2sMemory limit128 MB
Judgeable
Counting VowelsEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Rugby ClubEasy1
ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Cutting ChocolateEasy1
Math, ImplementationNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Print Stars - 3Easy1
ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Oven ClockEasy1
Math, SimulationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Average and MedianEasy1
Sorting, Array +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
MultiplicationEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
String RepetitionEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Least Common Multiple and Greatest Common DivisorEasy1
Math, Number theoryNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Typo Man Go ChangyoungEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Multiplication TableEasy1
ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Fibonacci NumberEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Leap YearEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
After the PartyEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
FBIEasy1
String, ImplementationNo attempts yetTime limit0.25sMemory limit128 MB
Judgeable
Alarm ClockEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
SangsuEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Completing a Chess SetEasy1
Array, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
ABCEasy1
Sorting, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
The Good and the BadEasy1
String, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Line NumbersEasy1
Implementation, StringNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Mirror, Oh! MirrorEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Spinner Lock SimulationEasy1
Simulation, Implementation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
TGN Advertising DecisionEasy1
Implementation, MathNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Triangle and Its Three SidesEasy1
Implementation, Math +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Divisors and MultiplesEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Even Sum Versus Odd SumEasy1
Array, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
BillingEasy1
Hash map, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Battle Droid PriceEasy1
Math, Implementation +2No attempts yetTime limit1sMemory limit128 MB
Judgeable
Entry Log ManagementEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
The Errand RouteEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
ReceiptEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
JOI and IOIEasy1
String, Brute force +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Exam ScoresEasy1
Implementation, MathNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Find the Students Who Didn't SubmitEasy1
Array, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Do-it, Do-it-NotEasy1
String, Implementation +1No attempts yetTime limit1sMemory limit128 MB
Judgeable
Reverse TextEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Sounds fishy!Easy1
Implementation, ArrayNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Which Alien?Easy1
Implementation, Brute force +1No attempts yetTime limit2sMemory limit512 MB
Judgeable
Multiple ChoiceEasy1
Array, ImplementationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
AlienEasy1
Geometry, Implementation +2No attempts yetTime limit2sMemory limit128 MB
Judgeable
FactorialEasy1
Math, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
LifeguardEasy1
Geometry, MathNo attempts yetTime limit1sMemory limit512 MB
Judgeable
Letter CounterEasy1
Array, StringNo attempts yetTime limit1sMemory limit512 MB
Judgeable
Long TapeEasy1
ArrayNo attempts yetTime limit1sMemory limit128 MB
Judgeable
FiguresEasy1
Sliding window, ArrayNo attempts yetTime limit1sMemory limit128 MB
Judgeable
WężykEasy1
Simulation, MatrixNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Flipping CoinsEasy1
Greedy, ArrayNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Caesar CipherEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
StrollEasy1
Simulation, MathNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Letter BankEasy1
Hash map, StringNo attempts yetTime limit1sMemory limit128 MB
Judgeable
First and Last LetterEasy1
StringNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Reverse Each WordEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Kkung's Space TripEasy1
Math, ImplementationNo attempts yetTime limit2sMemory limit128 MB
Judgeable
Fraud BustersEasy1
String matching, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Balloon ColorsEasy1
ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Birthday StatisticsEasy1
Array, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Encoding Binary NumbersEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Christmas Gift DrawEasy1
ArrayNo attempts yetTime limit2sMemory limit512 MB
Judgeable
GiftEasy1
Array, ImplementationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Morton NumbersEasy1
Bit manipulationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Gray codeEasy1
Bit manipulation, StringNo attempts yetTime limit1sMemory limit128 MB
Judgeable
Ship SelectionEasy1
Implementation, MathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
AcronymsEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Longest Run of X'sEasy1
ArrayNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Count VowelsEasy1
StringNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Golden Khon KaenEasy1
Hash mapNo attempts yetTime limit10sMemory limit64 MB
Judgeable
ServerEasy1
Prefix sum, SimulationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Subin and the SequenceEasy1
Prefix sum, MathNo attempts yetTime limit1sMemory limit32 MB
Judgeable
Mosquito TrapEasy1
GeometryNo attempts yetTime limit1sMemory limit32 MB
Judgeable
Keystrokes per FingerEasy1
Implementation, ArrayNo attempts yetTime limit1sMemory limit32 MB
Judgeable
Christmas PartyEasy1
ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Vertical ReadingEasy1
Simulation, Array +1No attempts yetTime limit1sMemory limit256 MB
Judgeable
Reversing Card SegmentsEasy1
Array, SimulationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Count ValueEasy1
ArrayNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Find the AlphabetEasy1
Array, StringNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Insert BallsEasy1
Array, SimulationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
The nth Fibonacci NumberEasy1
Dynamic programming, RecursionNo attempts yetTime limit1sMemory limit256 MB
Judgeable
N-orthotopeEasy1
Implementation, GeometryNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Palindrome CheckEasy1
String, Two pointersNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Use Every LetterEasy1
String, ArrayNo attempts yetTime limit2sMemory limit256 MB
Judgeable
Communication ChannelsEasy1
String, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Balancing WeightsEasy1
Implementation, MathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Logical Functions: AND and OREasy1
Simulation, ImplementationNo attempts yetTime limit2sMemory limit256 MB
Judgeable
Affine CipherEasy1
Implementation, String +1No attempts yetTime limit5sMemory limit256 MB
Judgeable
The Princess and the Magic MirrorEasy1
Matrix, ImplementationNo attempts yetTime limit2sMemory limit256 MB
Judgeable
PersistenceEasy1
Simulation, ImplementationNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Box intersection volumeEasy1
MathNo attempts yetTime limit1sMemory limit256 MB
Judgeable
CardsEasy1
ArrayNo attempts yetTime limit1sMemory limit32 MB
Judgeable
Power of TwoEasy1
Bit manipulationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Magic TrickEasy1
Array, ImplementationNo attempts yetTime limit5sMemory limit512 MB
Judgeable
George BooleEasy1
Implementation, String +2No attempts yetTime limit2sMemory limit512 MB
Judgeable
Hamming DistanceEasy1
Implementation, ArrayNo attempts yetTime limit1sMemory limit256 MB
Judgeable
Grass Seed Inc.Easy1
Math, ImplementationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
HandballEasy1
Array, ImplementationNo attempts yetTime limit2sMemory limit512 MB
Judgeable
Zero or OneEasy1
Implementation, Brute forceNo attempts yetTime limit1sMemory limit512 MB
Judgeable
The Y Bus Goes VroomEasy1
Simulation, Implementation +1No attempts yetTime limit2sMemory limit256 MB
Judgeable
Pick the QuadrantEasy1
Implementation, MathNo attempts yetTime limit1sMemory limit512 MB
Judgeable

Title	Level	Topics	Solved	Time limit	Memory limit	Judge
ResistanceGiven three color names, map each to its digit or multiplier using a fixed table and print the resulting resistance value.	Easy1	Hash mapImplementation	No attempts yet	2s	128 MB	Judgeable
Escape from a RectangleGiven a point inside an axis-aligned rectangle, compute the minimum distance from the point to the nearest side of the rectangle.	Easy1	MathGeometry+1	No attempts yet	2s	128 MB	Judgeable
Counting VowelsFor each input line until a terminating '#', count how many letters are vowels regardless of case.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Rugby ClubRead repeated name/age/weight lines until a sentinel and print whether each member is Senior or Junior based on simple thresholds.	Easy1	Implementation	No attempts yet	1s	128 MB	Judgeable
Cutting ChocolateCompute the minimum number of straight cuts needed to divide an N by M chocolate bar into all 1x1 pieces.	Easy1	MathImplementation	No attempts yet	2s	128 MB	Judgeable
Print Stars - 3Print N lines of stars where the count decreases from N down to 1.	Easy1	Implementation	No attempts yet	1s	128 MB	Judgeable
Oven ClockGiven a start time and a number of minutes to cook, compute and print the finishing time on a 24-hour clock.	Easy1	MathSimulation	No attempts yet	1s	128 MB	Judgeable
Average and MedianRead five natural numbers and print their average and median.	Easy1	SortingArray+1	No attempts yet	1s	128 MB	Judgeable
MultiplicationGiven two three-digit numbers, print the partial products from vertical multiplication and their total.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
String RepetitionGiven repeat count R and string S, output the string formed by repeating each character of S exactly R times in order.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Least Common Multiple and Greatest Common DivisorFor multiple integer pairs, compute and print each pair's least common multiple and greatest common divisor.	Easy1	MathNumber theory	No attempts yet	1s	128 MB	Judgeable
Typo Man Go ChangyoungGiven a string and a 1-based position, output the string with that one character removed, for multiple test cases.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Multiplication TablePrint the multiplication table for a given integer N from N1 to N9 in the exact required format.	Easy1	Implementation	No attempts yet	1s	128 MB	Judgeable
Fibonacci NumberCompute the nth Fibonacci number for n up to 45.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Leap YearGiven a year, output 1 if it is a leap year according to the standard divisibility rule, otherwise output 0.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
After the PartyCompute actual attendees as L times P, then output the difference between each of five reported counts and that value.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
FBIGiven five agent codes, print the 1-based positions of those containing the substring FBI, or a fixed message if none do.	Easy1	StringImplementation	No attempts yet	0.25s	128 MB	Judgeable
Alarm ClockGiven an alarm time in hours and minutes, compute and print the time 45 minutes earlier, wrapping around midnight if needed.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
SangsuReverse two given three-digit numbers digit by digit and print the larger reversed value.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Completing a Chess SetGiven counts of six white chess piece types, output how many of each must be added or removed to reach a complete 16-piece set.	Easy1	ArrayImplementation	No attempts yet	1s	128 MB	Judgeable
ABCSort three distinct numbers into A, B, C and print them in an order given by a 3-letter permutation string.	Easy1	SortingImplementation	No attempts yet	1s	128 MB	Judgeable
The Good and the BadCount the letters g and b in each hero name, ignoring case, and print whether the name is GOOD, A BADDY, or NEUTRAL.	Easy1	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Line NumbersRead N lines of text and print each one prefixed with its 1-based line number in the format "number. content".	Easy1	ImplementationString	No attempts yet	1s	128 MB	Judgeable
Mirror, Oh! MirrorRead lines of ASCII text until a line of three asterisks, and print each line with its characters reversed.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Spinner Lock SimulationGiven the starting digits of a spinner lock and a sequence of button labels, add each label's digits to the wheels modulo 10 and print the final readout.	Easy1	SimulationImplementation+2	No attempts yet	1s	128 MB	Judgeable
TGN Advertising DecisionFor each test case, compare the no-ad revenue r against e minus c, then print advertise, do not advertise, or does not matter.	Easy1	ImplementationMath	No attempts yet	1s	128 MB	Judgeable
Triangle and Its Three SidesRead triples of positive integers until 0 0 0, and for each print Equilateral, Isosceles, Scalene, or Invalid based on equal sides and the triangle inequality.	Easy1	ImplementationMath+1	No attempts yet	1s	128 MB	Judgeable
Divisors and MultiplesFor each pair of numbers, print factor if the first divides the second, multiple if the first is a multiple of the second, or neither.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
Even Sum Versus Odd SumFor each of up to 50 sequences, add the even numbers and the odd numbers separately and print EVEN, ODD, or TIE based on which sum is larger.	Easy1	ArrayImplementation	No attempts yet	1s	128 MB	Judgeable
BillingRead item names until EOI and print the total cost of all listed supplies with a dollar sign and two decimals.	Easy1	Hash mapImplementation	No attempts yet	1s	128 MB	Judgeable
Battle Droid PriceFor each test case, multiply five part quantities by fixed prices, sum them, and print the total with a dollar sign and two decimals.	Easy1	MathImplementation+2	No attempts yet	1s	128 MB	Judgeable
Entry Log ManagementRead N names and print each one converted to lowercase, one per line.	Easy1	StringImplementation	No attempts yet	1s	256 MB	Judgeable
The Errand RouteAdd four travel times given in seconds and print the total split into minutes on the first line and seconds on the second.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
ReceiptGiven the total price of 10 books and the prices of 9 of them, find the missing book's price.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
JOI and IOICount how many length-3 windows of a string equal JOI and how many equal IOI, including overlaps.	Easy1	StringBrute force+1	No attempts yet	1s	128 MB	Judgeable
Exam ScoresGiven the four subject scores of two students, print the larger of the two totals, or Minguk's total when they tie.	Easy1	ImplementationMath	No attempts yet	1s	128 MB	Judgeable
Find the Students Who Didn't SubmitGiven 28 distinct attendance numbers from 1 to 30, print the two missing numbers in increasing order.	Easy1	ArrayImplementation	No attempts yet	1s	128 MB	Judgeable
Do-it, Do-it-NotFor each test case, compare the two middle digits of an even-length binary string and print Do-it if they match, otherwise Do-it-Not.	Easy1	StringImplementation+1	No attempts yet	1s	128 MB	Judgeable
Reverse TextRead each test case line and print its characters in reverse order.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Sounds fishy!Read four depth readings and print Fish Rising, Fish Diving, Fish At Constant Depth, or No Fish based on their ordering.	Easy1	ImplementationArray	No attempts yet	2s	512 MB	Judgeable
Which Alien?Given the number of antennae and eyes a witness saw, print the names of all alien species whose ranges match, in the order given.	Easy1	ImplementationBrute force+1	No attempts yet	2s	512 MB	Judgeable
Multiple ChoiceRead a student's N answers followed by the N correct answers, and count how many positions match.	Easy1	ArrayImplementation	No attempts yet	2s	512 MB	Judgeable
AlienGiven a point and n axis-aligned rectangles, decide whether any rectangle contains the point, boundaries included.	Easy1	GeometryImplementation+2	No attempts yet	2s	128 MB	Judgeable
FactorialRead n and print the ones digit of n factorial.	Easy1	MathImplementation	No attempts yet	1s	128 MB	Judgeable
LifeguardThe task is to count children farther than k meters from the lifeguard position.	Easy1	GeometryMath	No attempts yet	1s	512 MB	Judgeable
Letter CounterCount how many times each letter appears across the given lines and print nonzero counts from a to z then A to Z.	Easy1	ArrayString	No attempts yet	1s	512 MB	Judgeable
Long TapeChoose a nonempty contiguous segment of the given sequence so its arithmetic mean is as small as possible.	Easy1	Array	No attempts yet	1s	128 MB	Judgeable
FiguresCheck whether any three consecutive figures contain one circle, one square, and one triangle.	Easy1	Sliding windowArray	No attempts yet	1s	128 MB	Judgeable
WężykPrint the numbers 1 to n squared in n rows that alternate between left-to-right and right-to-left order.	Easy1	SimulationMatrix	No attempts yet	1s	128 MB	Judgeable
Flipping CoinsCount the heads and tails and flip the coins on the less frequent side so all coins show the same face.	Easy1	GreedyArray	No attempts yet	1s	128 MB	Judgeable
Caesar CipherGiven the encrypted message and its original first letter, recover the shift and decode the full message.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
StrollGiven a walk of N, S, E and W steps on a grid, compute the Manhattan distance from the endpoint back to the start.	Easy1	SimulationMath	No attempts yet	2s	128 MB	Judgeable
Letter BankDecide whether the second word uses exactly the letters of the first word, each at least once.	Easy1	Hash mapString	No attempts yet	1s	128 MB	Judgeable
First and Last LetterPrint the first and last letter of each given uppercase string, doubling the letter for length 1.	Easy1	String	No attempts yet	1s	128 MB	Judgeable
Reverse Each WordFor each of T sentences, print the words in the same order with the letters inside every word reversed.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Kkung's Space TripCount the ships that reach the destination by checking whether each ship's fuel covers its burn rate over the travel time.	Easy1	MathImplementation	No attempts yet	2s	128 MB	Judgeable
Fraud BustersMatch each 9-character database code against the scanned code, treating every star as a wildcard, and print the matches in input order.	Easy1	String matchingImplementation	No attempts yet	1s	128 MB	Judgeable
Balloon ColorsCheck whether the first color differs from X and the last color differs from Y, then print BOTH, EASY, HARD, or OKAY.	Easy1	Implementation	No attempts yet	1s	128 MB	Judgeable
Birthday StatisticsCount how many of the n employees were born in each month and print the twelve monthly totals.	Easy1	ArrayImplementation	No attempts yet	1s	128 MB	Judgeable
Encoding Binary NumbersEncode each binary string as run lengths followed by digits and print the result per line.	Easy1	StringImplementation	No attempts yet	1s	128 MB	Judgeable
Christmas Gift DrawGiven the gift each guest drew, print for every guest who received the gift they brought.	Easy1	Array	No attempts yet	2s	512 MB	Judgeable
GiftCount the days on which the recorded time is at least k milliseconds faster than the previous day.	Easy1	ArrayImplementation	No attempts yet	2s	512 MB	Judgeable
Morton NumbersRead integers x and y and print their Morton number, built by interleaving the bits of x and y.	Easy1	Bit manipulation	No attempts yet	2s	512 MB	Judgeable
Gray codeConvert an n-bit binary string to its standard Gray code by copying the first bit and adding each adjacent pair of bits without carry.	Easy1	Bit manipulationString	No attempts yet	1s	128 MB	Judgeable
Ship SelectionCount the ships whose fuel covers consumption times the integer-division travel time for the given distance.	Easy1	ImplementationMath	No attempts yet	1s	256 MB	Judgeable
AcronymsGiven an acronym and candidate phrases, print the phrases whose word initials match the acronym letters in order.	Easy1	StringImplementation	No attempts yet	1s	256 MB	Judgeable
Longest Run of X'sCount the longest run of consecutive X marks in each hallway and print its length in the required sentence.	Easy1	Array	No attempts yet	1s	256 MB	Judgeable
Count VowelsCount the vowels a, e, i, o, and u in each given lowercase word and print the result in the required sentence.	Easy1	String	No attempts yet	1s	256 MB	Judgeable
Golden Khon KaenCount how many times the word GOLDEN can be formed from each given string of capital letters.	Easy1	Hash map	No attempts yet	10s	64 MB	Judgeable
ServerCount how many jobs from the front finish in request order before their total duration exceeds T.	Easy1	Prefix sumSimulation	No attempts yet	1s	256 MB	Judgeable
Subin and the SequenceGiven the prefix averages of a sequence, recover the original sequence term by term.	Easy1	Prefix sumMath	No attempts yet	1s	32 MB	Judgeable
Mosquito TrapFind the smallest area of an axis-aligned square that covers all given points on the table.	Easy1	Geometry	No attempts yet	1s	32 MB	Judgeable
Keystrokes per FingerCount how many times each of the eight fingers presses a key when the given string is typed on the fixed US layout.	Easy1	ImplementationArray	No attempts yet	1s	32 MB	Judgeable
Christmas PartyTally each friend's score over M guessing games from the targets and the written names.	Easy1	Implementation	No attempts yet	1s	256 MB	Judgeable
Vertical ReadingRead five given words column by column from top to bottom, skipping missing letters in shorter words, and print the letters in that order.	Easy1	SimulationArray+1	No attempts yet	1s	256 MB	Judgeable
Reversing Card SegmentsReverse ten given segments of a 20-card row that starts in order and print the final arrangement.	Easy1	ArraySimulation	No attempts yet	1s	256 MB	Judgeable
Count ValueCount how many times the integer v appears among the N given integers.	Easy1	Array	No attempts yet	1s	256 MB	Judgeable
Find the AlphabetGiven a lowercase word of length at most 100, output the 0-based first index of each letter a to z, or -1 when absent.	Easy1	ArrayString	No attempts yet	1s	256 MB	Judgeable
Insert BallsFill N baskets by writing ball number k into baskets i through j for each operation, then print all baskets.	Easy1	ArraySimulation	No attempts yet	1s	256 MB	Judgeable
The nth Fibonacci NumberGiven n up to 20, compute the nth Fibonacci number defined from 0 and 1.	Easy1	Dynamic programmingRecursion	No attempts yet	1s	256 MB	Judgeable
N-orthotopeGiven two axis-aligned boxes in N dimensions, print the dimension of their overlap, or -1 when they do not meet.	Easy1	ImplementationGeometry	No attempts yet	1s	256 MB	Judgeable
Palindrome CheckCheck whether the given lowercase word reads the same forward and backward and print 1 or 0.	Easy1	StringTwo pointers	No attempts yet	1s	256 MB	Judgeable
Use Every LetterDecide for each of up to 50 sentences whether it contains every letter a to z, and list the missing letters otherwise.	Easy1	StringArray	No attempts yet	2s	256 MB	Judgeable
Communication ChannelsCompare each transmitted binary string with its received copy and print OK when they match and ERROR otherwise.	Easy1	StringImplementation	No attempts yet	1s	256 MB	Judgeable
Balancing WeightsYou sum the signed positions of the weights and report whether the lever tips left, tips right, or stays balanced.	Easy1	ImplementationMath	No attempts yet	1s	256 MB	Judgeable
Logical Functions: AND and ORCheck each submitted weight and bias by testing all four binary inputs and report whether the neuron matches the requested AND or OR gate.	Easy1	SimulationImplementation	No attempts yet	2s	256 MB	Judgeable
Affine CipherApply E(X) = (aX + b) mod 26 to each uppercase letter of the plaintext and print the ciphertext.	Easy1	ImplementationString+1	No attempts yet	5s	256 MB	Judgeable
The Princess and the Magic MirrorPrint an N by N picture unchanged, mirrored left to right, or flipped top to bottom according to the given mood number.	Easy1	MatrixImplementation	No attempts yet	2s	256 MB	Judgeable
PersistenceCount how many times multiplying the decimal digits together reduces the given number to a single digit.	Easy1	SimulationImplementation	No attempts yet	1s	256 MB	Judgeable
Box intersection volumeCompute the volume shared by N axis-aligned boxes by intersecting their x, y, and z ranges.	Easy1	Math	No attempts yet	1s	256 MB	Judgeable
CardsTwo cards are compared at a time with the smaller pocketed, so find the largest possible sum of pocketed numbers for the given row.	Easy1	Array	No attempts yet	1s	32 MB	Judgeable
Power of TwoPrint 1 if the given natural number N is a power of two and 0 otherwise.	Easy1	Bit manipulation	No attempts yet	2s	512 MB	Judgeable
Magic TrickFind the card shared by the chosen rows of two 4 by 4 layouts, or report a bad layout or cheating.	Easy1	ArrayImplementation	No attempts yet	5s	512 MB	Judgeable
George BooleRead one boolean operation in the form true AND false and print its result.	Easy1	ImplementationString+2	No attempts yet	2s	512 MB	Judgeable
Hamming DistanceRead two n-dimensional integer vectors and count the positions where their entries differ.	Easy1	ImplementationArray	No attempts yet	1s	256 MB	Judgeable
Grass Seed Inc.Given the cost per square metre and a list of rectangular lawns, print the total cost of seeding all of them, rounded to seven decimals.	Easy1	MathImplementation	No attempts yet	2s	512 MB	Judgeable
HandballGiven each player's goal counts across M matches, count how many players scored at least once in every match.	Easy1	ArrayImplementation	No attempts yet	2s	512 MB	Judgeable
Zero or OneGiven three bits picked by three players, print the player whose bit differs from the other two, or * if there is no such player.	Easy1	ImplementationBrute force	No attempts yet	1s	512 MB	Judgeable
The Y Bus Goes VroomSimulate the passenger count as a bus travels N stops with given boarding and alighting numbers, then print the driver's fixed name.	Easy1	SimulationImplementation+1	No attempts yet	2s	256 MB	Judgeable
Pick the QuadrantRead the x and y coordinates of a nonzero point and print which of the four quadrants it lies in.	Easy1	ImplementationMath	No attempts yet	1s	512 MB	Judgeable