All Articles - Hazrat Ali Problem Solving

Jul 01, 2025 • Codeforces

Unique Bid Auction

There is a game called "Unique Bid Auction". You can read more about it here

Jul 01, 2025 • Leetcode

Binary Tree Maximum Path Sum

A path in a binary tree is a sequence of nodes where each pair of adjacent nodes in the sequence has an edge connecting them

Jul 01, 2025 • Codechef

Minimum number of Flips

Chef has an array A of length N consisting of 1−1 only.

Jun 30, 2025 • Codeforces

Pizza, Pizza, Pizza

Katie, Kuro and Shiro are best friends. They have known each other since kindergarten

Jun 30, 2025 • Leetcode

Construct Binary Tree from Preorder and Inorder Traversal

Given two integer arrays preorder and inorder where preorder is the preorder traversal of a binary tree

Jun 30, 2025 • Codechef

Get Lowest Free

Chef goes to the supermarket to buy some items. Luckily there's a sale going on under which Chef gets the following offer

Jun 29, 2025 • Leetcode

Most Frequent Subtree Sum

Given the root of a binary tree, return the most frequent subtree sum. If there is a tie, return all the values with the highest frequency in any order.

Jun 29, 2025 • Codechef

Chef And Operators

Chef has just started Programming,

Jun 29, 2025 • Codeforces

LCM

Ivan has number b He is sorting through the numbers a from 1

Jun 28, 2025 • Codeforces

Badge

In Summer Informatics School, if a student doesn't behave well, teachers make a hole in his badge. And today one of the teachers caught a group of n students

Jun 28, 2025 • Leetcode

Binary Tree Zigzag Level Order Traversal

Given the root of a binary tree, return the zigzag level order traversal of its nodes' values. (i.e., from left to right, then right to left for the next level

Jun 28, 2025 • Codechef

Reach fast

Chef is standing at coordinate A while Chefina is standing at coordinate B.

Jun 27, 2025 • Leetcode

Best Time to Buy and Sell Stock with Transaction Fee

You are given an array prices where prices[i] is the price of a given stock on the ith day, and an integer fee representing a transaction fee.

Jun 27, 2025 • Codeforces

QAQ

QAQ" is a word to denote an expression of crying. Imagine "Q" as eyes with tears and "A" as a mouth.

Jun 27, 2025 • Codechef

Mutated Minions

Gru has not been in the limelight for a long time and is, therefore, planning something particularly nefarious. Frustrated by his minions' incapability.

Jun 26, 2025 • Codeforces

Odds and Ends

Where do odds begin, and where do they end? Where does hope emerge, and will they ever break?

Jun 26, 2025 • Leetcode

Ugly Number II

An ugly number is a positive integer whose prime factors are limited to 2, 3, and 5.

Jun 26, 2025 • Codechef

Possible Victory

the team gets to play 6 times, and in each of these 6 tries, they can score a maximum of 6 runs.

Jun 25, 2025 • Codeforces

Birthday

Ivan is collecting coins. There are only N different collectible coins, Ivan has K of them

Jun 25, 2025 • Leetcode

Power of Four

Given an integer n, return true if it is a power of four. Otherwise, return false.

Jun 25, 2025 • Codechef

Dracula Eats

There are N spooky days left until Halloween.

Jun 24, 2025 • Leetcode

Search in Rotated Sorted Array

There is an integer array nums sorted in ascending order (with distinct values).

Jun 24, 2025 • Codechef

Endless Appetizers

Life is a like a box of of mozzarella sticks. You never know what you're gonna get.

Jun 23, 2025 • Codeforces

Trailing Loves (or L'oeufs?)

Aki is fond of numbers, especially those with trailing zeros

Jun 23, 2025 • HackerRank

Preorder Traversal

It must print the values in the tree's preorder traversal as a single line of space-separated values.

Jun 23, 2025 • Leetcode

Divide Two Integers

Given two integers dividend and divisor, divide two integers without using multiplication, division, and mod operator.

Jun 23, 2025 • Codechef

Presents for Cheffina

Chef has fallen in love with Cheffina, and wants to buy N gifts for her

Jun 22, 2025 • HackerRank

Postorder Traversal

Complete the function in the editor below. It received parameter: a pointer to the root of a binary tree. It must print the values in the tree's postorder.

Jun 22, 2025 • Codeforces

The Monster

A monster is chasing after Rick and Morty on another planet. They're so frightened that sometimes they scream

Jun 22, 2025 • Leetcode

Total Hamming Distance

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.

Jun 22, 2025 • Codechef

Chef and Races

The National Championships are starting soon. There are 4 race categories.

Jun 21, 2025 • HackerRank

Level Order Traversal

Given a pointer to the root of a binary tree, you need to print the level order traversal of this tree

Jun 21, 2025 • Codeforces

Okabe and Banana Trees

Okabe needs bananas for one of his experiments for some strange reason. So he decides to go to the forest and cut banana trees.

Jun 21, 2025 • Leetcode

Nth Digit

Given an integer n, return the nth digit of the infinite integer sequence [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...].

Jun 21, 2025 • Codechef

Chef Fantasy 11

All of Chef's friends are playing fantasy cricket based upon the ODI World Cup, and Chef would like to join them.

Jun 20, 2025 • Leetcode

Factorial Trailing Zeroes

Given an integer n, return the number of trailing zeroes in n.

Jun 20, 2025 • Codechef

Building Race

Two friends Chef and Chefina are currently on floors A and B respectively.

Jun 19, 2025 • Codechef

Too many items

Chef bought N items from a shop. Although it is hard to carry all these items in hand, so Chef has to buy some polybags to store these items.

Jun 19, 2025 • HackerRank

Inorder Traversal

In this challenge, you are required to implement inorder traversal of a tree.

Jun 19, 2025 • Codeforces

Got Any Grapes

For simplicity, we'll assume that there are only three types of grapes: green grapes, purple grapes and black grapes.

Jun 19, 2025 • Leetcode

Keys and Rooms

There are n rooms labeled from 0 to n 1 and all the rooms are locked except for room

Jun 18, 2025 • Codeforces

Definite Game

Chouti was doing a competitive programming competition.

Jun 18, 2025 • HackerRank

Height of a Binary Tree

The height of a binary tree is the number of edges between the tree's root and its furthest leaf.

Jun 18, 2025 • Leetcode

Generate Parentheses

Given n pairs of parentheses, write a function to generate all combinations of well-formed parentheses.

Jun 18, 2025 • Codeforces

Elections

Elections are taking place in Berland. There are n candidates participating in the elections, numbered from 1 to n

Jun 18, 2025 • Codechef

Cyclic Quadrilateral

Read problem statements in Mandarin Chinese, Russian, and Vietnamese as well.

Jun 17, 2025 • Codechef

A or B

It is known that Chef requires X minutes to solve Problem A correctly and Y minutes to solve Problem B correctly.

Jun 17, 2025 • Leetcode

Restore IP Addresses

A valid IP address consists of exactly four integers separated by single dots. Each integer is between.

Jun 16, 2025 • HackerRank

Binary Search Tree Insertion

You are given a pointer to the root of a binary search tree and values to be inserted into the tree.

Jun 16, 2025 • Codeforces

Packets

You have n coins, each of the same value of 1.

Jun 16, 2025 • Codechef

Airlines

An airline operates X aircraft every day. Each aircraft can carry up to 100 passengers.

Jun 16, 2025 • Leetcode

Excel Sheet Column Title

Given an integer column Number, return its corresponding column title as it appears in an Excel sheet.

Jun 15, 2025 • Codechef

Too many Floors

Chef and Chefina are residing in a hotel.

Jun 15, 2025 • Leetcode

Binary Tree Right Side View

Given the root of a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

Jun 15, 2025 • HackerRank

Maximum Element

You have an empty sequence, and you will be given queries. Each query is one of these three types.

Jun 15, 2025 • Codeforces

Chess For Three

Alex, Bob and Carl will soon participate in a team chess tournament.

Jun 14, 2025 • HackerRank

Inserting a Node Into a Sorted Doubly Linked List

Given a reference to the head of a doubly-linked list and an integer.

Jun 14, 2025 • Codeforces

Function Height

The given points are vertices of a plot of a piecewise function. The j-th piece of the function is the segment PjPj+1

Jun 14, 2025 • Leetcode

Redundant Connection

In this problem, a tree is an undirected graph that is connected and has no cycles.

Jun 14, 2025 • Codechef

Chef Eren

Chef is a very big fan of Eren Yeager.

Jun 13, 2025 • HackerRank

Print the Elements of a Linked List

This exercise focuses on traversing a linked list.

Jun 13, 2025 • Codeforces

Coins

In Berland, there are two types of coins, having denominations of 2and k burles

Jun 13, 2025 • Leetcode

My Calendar I

You are implementing a program to use as your calendar. We can add a new event if adding the event will not cause a double booking.

Jun 12, 2025 • Codeforces

Love Triangle

As you could know there are no male planes nor female planes. However

Jun 12, 2025 • HackerRank

Reverse a linked list

Given the pointer to the head node of a linked list, change the next pointers of the nodes so that their order is reversed.

Jun 12, 2025 • Leetcode

Maximal Rectangle

Given a rows x cols binary matrix filled with 0's and 1's, find the largest rectangle containing

Jun 12, 2025 • Codechef

It is My Serve

Alice and Bob are playing a game of table tennis where irrespective of the point scored.

Jun 11, 2025 • HackerRank

Insert a Node at the Tail of a Linked List

You are given the pointer to the head node of a linked list and an integer to add to the list.

Jun 11, 2025 • Codeforces

Benches

There are n benches in the Berland Central park. It is known that a people are currently sitting on the bench

Jun 11, 2025 • Leetcode

First Missing Positive

Given an unsorted integer array nums. Return the smallest positive integer that is not present in nums.

Jun 11, 2025 • Codechef

Blackjack

Chef is playing a variant of Blackjack, where 3 numbers are drawn and each number lies between

Jun 10, 2025 • HackerRank

Insert a node at the head of a linked list

Given a pointer to the head of a linked list, insert a new node before the head

Jun 10, 2025 • Codeforces

Cloning Toys

Recently, he found a machine that can clone plush toys

Jun 10, 2025 • Leetcode

Validate Binary Search Tree

Given the root of a binary tree, determine if it is a valid binary search tree (BST).

Jun 10, 2025 • Codechef

Chess Ratings

Alice has recently started playing Chess. Her current rating is X. She noticed that when she wins a game, her rating increases by 8 points.

Jun 09, 2025 • HackerRank

Find Merge Point of Two Lists

Given pointers to the head nodes of linked lists that merge together at some point.

Jun 09, 2025 • Codeforces

Between the Offices

As you may know, MemSQL has American offices in both San Francisco and Seattle

Jun 09, 2025 • Leetcode

Different Ways to Add Parentheses

Given a string expression of numbers and operators, return all possible results from computing all the different possible ways to group numbers and operators.

Jun 09, 2025 • Codechef

Complementary Strand in a DNA

You are given the sequence of Nucleotides of one strand of DNA through a string

Jun 08, 2025 • Codeforces

Numbers on the Chessboard

You are given a chessboard of size n×n It is filled with numbers from 1 to n2

Jun 08, 2025 • HackerRank

Print in Reverse

Given a pointer to the head of a singly-linked list, print each value from the reversed list. If the given list is empty, do not print anything.

Jun 08, 2025 • Leetcode

Find Mode in Binary Search Tree

Given the root of a binary search tree (BST) with duplicates, return all the mode(s) (i.e., the most frequently occurred element) in it.

Jun 08, 2025 • Codechef

Mario and Bullet

Mario's bullet moves at X pixels per frame. He wishes to shoot a goomba standing Y pixels away from him. The goomba does not move.

Jun 07, 2025 • Codeforces

Chips Moving

You are given n chips on a number line. The i-th chip is placed at the integer coordinate

Jun 07, 2025 • Codechef

Police and Thief

Chef discovered that his secret recipe has been stolen. He immediately informs the police of the theft.

Jun 07, 2025 • Leetcode

Second Minimum Node In a Binary Tree

Given a non-empty special binary tree consisting of nodes with the non-negative value.

Jun 06, 2025 • Codeforces

Heist

There was an electronic store heist last night.

Jun 06, 2025 • Leetcode

Binary Tree Level Order Traversal

Given the root of a binary tree, return the level order traversal of its nodes' values. (i.e., from left to right, level by level).

Jun 06, 2025 • Codechef

Mario and Transformation

Mario transforms each time he eats a mushroom as follows

Jun 05, 2025 • HackerRank

Delete duplicate-value nodes from a sorted linked list

You are given the pointer to the head node of a sorted linked list, where the data in the nodes is in ascending order.

Jun 05, 2025 • Codeforces

Wrong Subtraction

Little girl Tanya is learning how to decrease a number by one

Jun 05, 2025 • Codechef

Maximise the Tastiness

Chef is making a dish that consists of exactly two ingredients. He has four ingredients.

Jun 05, 2025 • Leetcode

Trim a Binary Search Tree

Given the root of a binary search tree and the lowest and highest boundaries as low and high

Jun 04, 2025 • Codeforces

Splits

Let's define a split of n as a nonincreasing sequence of positive integers, the sum of which is n

Jun 04, 2025 • Leetcode

Maximum Binary Tree

You are given an integer array nums with no duplicates. A maximum binary tree can be built recursively from nums using the following algorithm.

Jun 04, 2025 • Codechef

Bus Seat Numbering

There is a bus with 30 seats. The seats are numbered from 1 to 30, and the numbering is as depicted in this image.

Jun 03, 2025 • Codeforces

Piles With Stones

There is a beautiful garden of stones in Innopolis.

Jun 03, 2025 • Leetcode

Smallest Subtree with all the Deepest Nodes

Given the root of a binary tree, the depth of each node is the shortest distance to the root.

Jun 03, 2025 • Codechef

Jenga Night

Chef hosts a party for his birthday. There are N people at the party. All these N people decide to play Jenga.

Jun 02, 2025 • HackerRank

Balanced Brackets

A bracket is considered to be any one of the following characters: (, ), {, }, [, or ].

Jun 02, 2025 • Codeforces

Pizza, Pizza, Pizza!!!

Katie, Kuro and Shiro are best friends. They have known each other since kindergarten

Jun 02, 2025 • Leetcode

Find Largest Value in Each Tree Row

Given the root of a binary tree, return an array of the largest value in each row of the tree (0-indexed).

Jun 02, 2025 • Codechef

Chef and Candies

There are N children and Chef wants to give them1 candy each. Chef already has X

Jun 01, 2025 • Codeforces

Water Lily

While sailing on a boat, Inessa noticed a beautiful water lily flower above the lake's surface

Jun 01, 2025 • HackerRank

Insert a node at a specific position in a linked list

Given a pointer to the head node of a linked list and an integer to insert at a certain position

Jun 01, 2025 • Leetcode

Sum Root to Leaf Numbers

You are given the root of a binary tree containing digits from 0 to 9 only.

Jun 01, 2025 • Codechef

Expert Setter

A problem setter is called an expert if at least 50% of their problems are approved by Chef.

May 31, 2025 • Codeforces

Disturbed People

There is a house with n flats situated on the main street of Berlatov.

May 31, 2025 • Leetcode

Subtree of Another Tree

Given the roots of two binary trees root and subRoot, return true if there is a subtree of root with the same structure and node values of subRoot and false.

May 31, 2025 • Codechef

Water Filling

Chef has three water bottles. At any point, if at least two of them are empty.

May 30, 2025 • Codeforces

Dice Rolling

Mishka got a six-faced dice. It has integer numbers from 2 to 7 written on its faces

May 30, 2025 • HackerRank

Delete a Node

Delete the node at a given position in a linked list and return a reference to the head node

May 30, 2025 • Hackathon

Addition Errors

Bob is a noob mathematician and he is not very comfortable with addition of numbers

May 30, 2025 • Leetcode

Kth Smallest Element in a BST

Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) of all the values of the nodes in the tree.

May 30, 2025 • Codechef

Exams

In Chefland, there are X schools, and each school has Y students.

May 29, 2025 • Codeforces

File Name

You can not just take the file and send it. When Polycarp trying to send a file in the social network.

May 29, 2025 • Codechef

Sasta Shark Tank

Devendra just had a million-dollar idea and he needs funds to startup. He was recently invited to Sasta Shark Tank (A TV show where entrepreneurs pitch.

May 29, 2025 • Leetcode

Delete Node in a BST

Given a root node reference of a BST and a key, delete the node with the given key in the BST. Return the root node reference (possibly updated) of the BST.

May 28, 2025 • Hackathon

Number of cycles

You are given an N-sided regular polygon. You have connected the center of the polygon with all the vertices, thus dividing the polygon into N equal parts.

May 28, 2025 • Codeforces

Polycarp's Pockets

Polycarp has n coins, the value of coin is Polycarp wants to distribute all the coins between his pockets

May 28, 2025 • HackerRank

Cycle Detection

A linked list is said to contain a cycle if any node is visited more than once while traversing the list.

May 28, 2025 • Leetcode

Binary Tree Postorder Traversal

Given the root of a binary tree, return the postorder traversal of its nodes' values.

May 28, 2025 • Codechef

Binary Battles

N teams have come to participate in a competitive coding event called “Binary Battles

May 27, 2025 • Hackathon

Alice and Bob buy crackers

Alice and Bob want to buy firecrackers. There are types of firecrackers available in the market

May 27, 2025 • HackerRank

Get Node Value

Given a pointer to the head of a linked list and a specific position, determine the data value at that position

May 27, 2025 • Codeforces

New Year and the Christmas Ornament

Alice and Bob are decorating a Christmas Tree.

May 27, 2025 • Leetcode

Longest Univalue Path

Given the root of a binary tree, return the length of the longest path, where each node in the path has the same value. This path may or may not pass through.

May 27, 2025 • Codechef

Cup Finals

It is the World Cup Finals. Chef only finds a match interesting if the skill difference of the competing teams is less than or equal to D.

May 26, 2025 • Codeforces

Greedy Arkady

k people want to split n candies between them. Each candy should be given to exactly one of them or be thrown away.

May 26, 2025 • HackerRank

Compare two linked lists

You’re given the pointer to the head nodes of two linked lists. Compare the data in the nodes of the linked lists to check if they are equal. If all data.

May 26, 2025 • Leetcode

Univalued Binary Tree

A binary tree is uni-valued if every node in the tree has the same value.

May 26, 2025 • Codechef

Recent contest problems

CodeChef recently revamped its practice page to make it easier for users to identify the next problems they should solve by introducing some new features.

May 25, 2025 • HackerRank

Reverse a doubly linked list

Given the pointer to the head node of a doubly linked list, reverse the order of the nodes in place.

May 25, 2025 • Codeforces

Maxim Buys an Apartment

Maxim wants to buy an apartment in a new house at Line Avenue of Metropolis.

May 25, 2025 • Leetcode

Lowest Common Ancestor of a Binary Tree

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

May 25, 2025 • Codechef

Minimum number of coins

Chef has infinite coins in denominations of rupees 5 and rupees 10.

May 24, 2025 • Codeforces

Adjacent Replacements

Mishka got an integer array a of length n as a birthday present (what a surprise!).

May 24, 2025 • Codechef

Small Factorial

Write a program to find the factorial value of any number entered by the user.

May 24, 2025 • HackerRank

2D Array - DS

Given a 2D array, an hourglass is a subset of values with indices falling in the following pattern

May 24, 2025 • Leetcode

Convert Sorted Array to Binary Search Tree

Given an integer array nums where the elements are sorted in ascending order, convert it to a height-balanced binary search tree.

May 23, 2025 • Codeforces

Equator

Polycarp has created his own training plan to prepare for the programming contests. He will train for n days, all days are numbered from 1 to n beginning

May 23, 2025 • HackerRank

Arrays - DS

An array is a data structure that stores elements of the same type in a contiguous block of memory

May 23, 2025 • Leetcode

Binary Tree Paths

Given the root of a binary tree, return all root-to-leaf paths in any order.

May 23, 2025 • Codechef

X Jumps

Chef is currently standing at stair 0 and he wants to reach stair numbered X.

May 22, 2025 • HackerRank

Breadth First Search Shortest Reach

Consider an undirected graph where each edge weighs 6 units. Each of the nodes is labeled consecutively from 1

May 22, 2025 • Codeforces

Find Amir

A few years ago Sajjad left his school and register to another one due to security reasons. Now he wishes to find Amir, one of his schoolmates and good friends.

May 22, 2025 • Leetcode

Find Bottom Left Tree Value

Given the root of a binary tree, return the leftmost value in the last row of the tree.

May 22, 2025 • Codechef

Second Largest

Three numbers A, B and C are the inputs. Write a program to find second largest among them.

May 21, 2025 • Codechef

Fill Candies

Chef received N candies on his birthday. He wants to put these candies in some bags. A bag has K pockets and each pocket can hold at most M candies

May 21, 2025 • Codeforces

Magic Forest

Imp is in a magic forest, where xorangles grow (wut?)

May 21, 2025 • Leetcode

Convert BST to Greater Tree

Given the root of a Binary Search Tree (BST), convert it to a Greater Tree such that every key of the original BST is changed to the original key plus the sum.

May 20, 2025 • Codeforces

Beautiful Divisors

Recently Luba learned about a special kind of numbers that she calls beautiful numbers.

May 20, 2025 • HackerRank

Forming a Magic Square

We define a magic square to be an matrix of distinct positive integers from to where the sum of any row, column, or diagonal of length is always equal

May 20, 2025 • Leetcode

Diameter of Binary Tree

Given the root of a binary tree, return the length of the diameter of the tree.

May 20, 2025 • Codechef

Chefland Games

Each referee has to point out whether he considers the ball to be inside limits or outside limits. The ball is considered to be IN if and only if all the.

May 19, 2025 • Codeforces

Paper Airplanes

To make a paper airplane, one has to use a rectangular piece of paper. From a sheet of standard size you can make s airplanes.

May 19, 2025 • HackerRank

Minimum Distances

The distance between two array values is the number of indices between them. Given , find the minimum distance between any pair of equal elements in the array.

May 19, 2025 • Leetcode

Minimum Depth of Binary Tree

Given a binary tree, find its minimum depth.

May 19, 2025 • Codechef

The Lead Game

The game of billiards involves two players knocking 3 balls around on a green baize table. Well, there is more to it, but for our purposes this is sufficient.

May 18, 2025 • Codeforces

Diagonal Walking

Mikhail walks on a 2D plane. He can go either up or right. You are given a sequence of Mikhail's moves. He thinks that this sequence is too long and he wants.

May 18, 2025 • Leetcode

Binary Tree Inorder Traversal

Given the root of a binary tree, return the inorder traversal of its nodes' values.

May 18, 2025 • Codechef

Qualify the round

In a coding contest, there are two types of problems

May 17, 2025 • Codeforces

Maximize Sum of Digits

Anton has the integer x. He is interested what positive integer, which doesn't exceed x, has the maximum sum of digits.

May 17, 2025 • Leetcode

Same Tree

Given the roots of two binary trees p and q, write a function to check if they are the same or not.

May 17, 2025 • Codechef

Pass or Fail

Chef is struggling to pass a certain college course.

May 16, 2025 • HackerRank

The Time in Words

Given the time in numerals we may convert it into words, as shown below

May 16, 2025 • Codeforces

Splits

Let's define a split of n as a nonincreasing sequence of positive integers, the sum of which is n

May 16, 2025 • Leetcode

Path Sum

Given the root of a binary tree and an integer targetSum, return true if the tree has a root-to-leaf path.

May 16, 2025 • Codechef

Self Defence Training

After the phenomenal success of the 36th Chamber of Shaolin, San Te has decided to start 37th Chamber of Shaolin. The aim this time is to equip women

May 15, 2025 • Codeforces

Hit the Lottery

Allen has a LOT of money. He has n dollars in the bank

May 15, 2025 • HackerRank

Service Lane

A driver is driving on the freeway. The check engine light of his vehicle is on, and the driver wants to get service immediately.

May 15, 2025 • Leetcode

Maximum Depth of Binary Tree

Given the root of a binary tree, return its maximum depth.

May 15, 2025 • Codechef

Watching Movies at 2x

Chef started watching a movie that runs for a total of X minutes.

May 14, 2025 • Codeforces

Borya's Diagnosis

It seems that Borya is seriously sick. He is going visit n doctors to find out the exact diagnosis

May 14, 2025 • Leetcode

Balanced Binary Tree

Given a binary tree, determine if it is height-balanced.

May 14, 2025 • Codechef

Decrement OR Increment

Write a program to obtain a number N and increment its value by 1 if the number is divisible by 4 otherwise decrement its value by 1.

May 13, 2025 • Codeforces

Mahmoud and Ehab and the even-odd game

Mahmoud and Ehab play a game called the even-odd game. Ehab chooses his favorite integer n and then they take turns

May 13, 2025 • HackerRank

Number Line Jumps

You are choreographing a circus show with various animals. For one act, you are given two kangaroos on a number line ready to jump in the positive direction.

May 13, 2025 • Leetcode

Gray Code

An n-bit gray code sequence is a sequence of 2n integers where:

May 13, 2025 • Codechef

Chef and Water Bottles

Chef has N empty bottles where each bottle has a capacity of X litres.

May 12, 2025 • Codeforces

Chess For Three

Three friends gathered to play a few games of chess together

May 12, 2025 • HackerRank

Lonely Integer

Given an array of integers, where all elements but one occur twice, find the unique element.

May 12, 2025 • Leetcode

Permutations

Given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

May 12, 2025 • Codechef

Candy Distribution

Chef has N candies. He has to distribute them to exactly M of his friends such that each friend gets equal number of candies and each friend gets even num.

May 11, 2025 • Codeforces

Mister B and Book Reading

Mister B once received a gift: it was a book about aliens, which he started read immediately. This book had c pages.

May 11, 2025 • HackerRank

Minimum Absolute Difference in an Array

The absolute difference is the positive difference between two values is written

May 11, 2025 • Codechef

Chessboard Distance

The Chessboard Distance for any two points.

May 11, 2025 • Leetcode

Combination Sum

Given an array of distinct integers candidates and a target integer target.

May 10, 2025 • Codeforces

If at first you don't succeed

Each student eagerly awaits the day he would pass the exams successfully

May 10, 2025 • Codechef

Weights

Chef is playing with weights. He has an object weighing W units.

May 10, 2025 • Leetcode

Sum of Square Numbers

Given a non-negative integer c, decide whether there're two integers a and b such that a2 + b2 = c.

May 09, 2025 • Codeforces

Hamster Farm

Dima has a hamsters farm. Soon N hamsters will grow up on it and Dima will sell them in a city nearby.

May 09, 2025 • HackerRank

Intro to Tutorial Challenges

Many of the challenges on HackerRank are difficult and assume that you already know the relevant algorithms.

May 09, 2025 • Leetcode

Ugly Number

An ugly number is a positive integer which does not have a prime factor other than 2, 3, and 5.

May 09, 2025 • Codechef

Speed Limit Test

Alice is driving from her home to her office which is A kilometers away and will take her X hours to reach.

May 08, 2025 • Codeforces

Fraction

Petya is a big fan of mathematics, especially its part related to fractions.

May 08, 2025 • HackerRank

Running Time of Algorithms

In a previous challenge you implemented the Insertion Sort algorithm. It is a simple sorting algorithm that works well with small or mostly sorted data.

May 08, 2025 • Leetcode

Roman to Integer

Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.

May 08, 2025 • Codechef

Water Mixing

Chef is setting up a perfect bath for himself. He has X litres of hot water and Y litres of cold water.

May 07, 2025 • HackerRank

Sales by Match

There is a large pile of socks that must be paired by color. Given an array of integers representing the color of each sock, determine how many pairs of socks.

May 07, 2025 • Codeforces

Bear and Different Names

In the army, it isn't easy to form a group of soldiers that will be effective on the battlefield. The communication is crucial and thus no two soldiers should

May 07, 2025 • Leetcode

Queue Reconstruction by Height

You are given an array of people, people, which are the attributes of some people in a queue (not necessarily in order)

May 07, 2025 • Codechef

The Last Levels

Chef is playing a videogame, and is getting close to the end. He decides to finish the rest of the game in a single session.

May 06, 2025 • Codeforces

Kirill And The Game

Kirill plays a new computer game. He came to the potion store where he can buy any potion. Each potion is characterized by two integers

May 06, 2025 • Leetcode

Jump Game

You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length.

May 06, 2025 • Codechef

Finding Square Roots

In olden days finding square roots seemed to be difficult but nowadays it can be easily done using in-built functions available across many languages

May 05, 2025 • HackerRank

Subarray Division

Two children, Lily and Ron, want to share a chocolate bar. Each of the squares has an integer on it.

May 05, 2025 • Codeforces

Kuro and Walking Route

Kuro is living in a country called Uberland consisting of n towns, numbered from 1 to n and n−1 bidirectional roads connecting these towns

May 05, 2025 • Leetcode

Gas Station

There are n gas stations along a circular route, where the amount of gas at the ith station is gas[i].

May 05, 2025 • Codechef

Small factorials

You are asked to calculate factorials of some small positive integers.

May 04, 2025 • HackerRank

Flipping bits

You will be given a list of 32 bit unsigned integers. Flip all the bits ( and ) and return the result as an unsigned integer.

May 04, 2025 • Codeforces

Commentary Boxes

Berland Football Cup starts really soon! Commentators from all over the world come to the event.

May 04, 2025 • Leetcode

Remove Nth Node From End of List

Given the head of a linked list, remove the nth node from the end of the list and return its head.

May 04, 2025 • Codechef

Finding Shoes

Chef has N friends. Chef promised that he would gift a pair of shoes (consisting of one left shoe and one right shoe) to each of his N friends

May 03, 2025 • Codeforces

Year of University Entrance

There is the faculty of Computer Science in Berland. In the social net "TheContact.

May 03, 2025 • HackerRank

Mark and Toys

Mark and Jane are very happy after having their first child. Their son loves toys

May 03, 2025 • Codechef

Bath in Winters

A geyser has a capacity of X litres of water and a bucket has a capacity of Y litres of water.

May 03, 2025 • Leetcode

Rotate List

Given the head of a linked list, rotate the list to the right by k places.

May 02, 2025 • HackerRank

Marc's Cakewalk

Marc loves cupcakes, but he also likes to stay fit. Each cupcake has a calorie count, and Marc can walk a distance to expend those calories.

May 02, 2025 • Codeforces

Diagonal Walking

Mikhail walks on a 2D plane. He can go either up or right. You are given a sequence of Mikhail's moves. He thinks that this sequence is too long and he wants.

May 02, 2025 • Leetcode

Merge Two Sorted Lists

You are given the heads of two sorted linked lists list1 and list2.

May 02, 2025 • Codechef

Flip the cards

There are N cards on a table, out of which X cards are face-up and the remaining are face-down.

May 01, 2025 • HackerRank

Insertion Sort - Part 2

In Insertion Sort Part 1, you inserted one element into an array at its correct sorted position. Using the same approach repeatedly, can you sort an entire.

May 01, 2025 • Codeforces

Fake NP

Tavak and Seyyed are good friends. Seyyed is very funny and he told Tavak to solve the following problem instead of longest-path.

May 01, 2025 • Codechef

Discus Throw

In discus throw, a player is given 3 throws and the throw with the longest distance is regarded as their final score.

May 01, 2025 • Leetcode

Escape The Ghosts

You are playing a simplified PAC-MAN game on an infinite 2-D grid. You start at the point

Apr 30, 2025 • HackerRank

Camel Case

There is a sequence of words in CamelCase as a string of letters, s, having the following properties:

Apr 30, 2025 • Leetcode

Diagonal Traverse

Given an m x n matrix mat, return an array of all the elements of the array in a diagonal order.

Apr 30, 2025 • Codechef

Test Score

In a test, there are N problems, each carrying X marks.

Apr 29, 2025 • HackerRank

Insertion Sort - Part 1

One common task for computers is to sort data. For example, people might want to see all their files on a computer sorted by size

Apr 29, 2025 • Codechef

Minimum Cars required

A single car can accommodate at most 4 people.

Apr 29, 2025 • Leetcode

Perfect Squares

Given an integer n, return the least number of perfect square numbers that sum to n.

Apr 28, 2025 • Codeforces

Equal Sums

You are given k sequences of integers. The length of the i-th sequence equals to ni .

Apr 28, 2025 • HackerRank

Missing Numbers

Given two arrays of integers, find which elements in the second array are missing from the first array.

Apr 28, 2025 • Codechef

Good Program

In computing, the collection of four bits is called a nibble

Apr 28, 2025 • Leetcode

Delete Operation for Two Strings

Given two strings word1 and word2, return the minimum number of steps required to make word1 and word2 the same.

Apr 27, 2025 • Codechef

Air Conditioner Temperature

There are three people sitting in a room - Alice, Bob, and Charlie. They need to decide on the temperature to set on the air.

Apr 27, 2025 • HackerRank

Grid Challenge

Given a square grid of characters in the range ascii[a-z], rearrange elements of each row alphabetically, ascending.

Apr 27, 2025 • Leetcode

Longest Consecutive Sequence

Given an unsorted array of integers nums, return the length of the longest consecutive elements sequence.

Apr 27, 2025 • Codeforces

Arya and Bran

Bran and his older sister Arya are from the same house. Bran like candies so much, so Arya is going to give him some Candies

Apr 26, 2025 • HackerRank

Recursive Digit Sum

We define super digit of an integer using the following rules

Apr 26, 2025 • Codeforces

Problems in your to-do list

CodeChef recently revamped its practice page to make it easier for users to identify the next problems they should solve by introducing some new features.

Apr 26, 2025 • Leetcode

Rotated Digits

An integer x is a good if after rotating each digit individually by 180 degrees, we get a valid number that is different from x. Each digit must be rotated.

Apr 26, 2025 • Codeforces

Shell Game

Bomboslav likes to look out of the window in his room and watch lads outside playing famous shell game.

Apr 25, 2025 • Leetcode

Bulls and Cows

You are playing the Bulls and Cows game with your friend.

Apr 25, 2025 • HackerRank

Alternating Characters

You are given a string containing characters A and B only. Your task is to change it into a string such that there are no matching adjacent characters.

Apr 25, 2025 • Codechef

The Three Topics

The Chef has reached the finals of the Annual Inter-school Declamation contest.

Apr 24, 2025 • Codeforces

3 Palindrome

In the beginning of the new year Keivan decided to reverse his name. He doesn't like palindromes, so he changed Naviek to Navick.

Apr 24, 2025 • Leetcode

Robot Return to Origin

There is a robot starting at the position (0, 0), the origin, on a 2D plane. Given a sequence of its moves, judge if this robot ends up at (0, 0).

Apr 24, 2025 • Codechef

Count the Notebooks

You know that 1 kg of pulp can be used to make 1000 pages and 1 notebook consists of 100 pages

Apr 23, 2025 • Codechef

Sugarcane Juice Business

While Alice was drinking sugarcane juice, she started wondering about the following facts

Apr 23, 2025 • HackerRank

Funny String

In this challenge, you will determine whether a string is funny or not. To determine whether a string is funny.

Apr 23, 2025 • Codeforces

Key races

Two boys decided to compete in text typing on the site "Key races". During the competition, they have to type a text consisting of s characters

Apr 23, 2025 • Leetcode

Isomorphic Strings

Given two strings s and t, determine if they are isomorphic.

Apr 23, 2025 • Leetcode

First Unique Character in a String

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Apr 22, 2025 • HackerRank

Palindrome Index

Given a string of lowercase letters in the range ascii[a-z], determine the index of a character that can be removed to make the string a palindrome.

Apr 22, 2025 • Codechef

Chef and NextGen

Chef is currently working for a secret research group called NEXTGEN. While the rest of the world is still in search of a way to utilize Helium.

Apr 22, 2025 • Leetcode

Compare Version Numbers

Given two version strings, version1 and version2, compare them. A version string consists of revisions separated by dots '.'. The value of the revision.

Apr 21, 2025 • HackerRank

Sherlock and the Valid String

Sherlock considers a string to be valid if all characters of the string appear the same number of times.

Apr 21, 2025 • Codechef

Sale Season

It's the sale season again and Chef bought items worth a total of X rupees. The sale season offer is as follows

Apr 21, 2025 • Leetcode

Add Strings

Given two non-negative integers, num1 and num2 represented as string, return the sum of num1 and num2 as a string.

Apr 20, 2025 • Codechef

Year of University Entrance

There is the faculty of Computer Science in Berland. In the social net "TheContact!" for each course of this faculty there is the special

Apr 20, 2025 • Leetcode

Magical String

A magical string s consists of only '1' and '2' and obeys the following rules

Apr 20, 2025 • HackerRank

Strong Password

Louise joined a social networking site to stay in touch with her friends. The signup page required her to input a name and a password

Apr 20, 2025 • Codechef

Minimum Pizzas

Each pizza consists of 4 slices. There are N friends and each friend needs exactly X slices.

Apr 19, 2025 • HackerRank

Pangrams

A pangram is a string that contains every letter of the alphabet. Given a sentence determine whether it is a pangram in the English alphabet

Apr 19, 2025 • Codeforces

Jon Snow and his Favourite Number

Jon Snow now has to fight with White Walkers. He has n rangers, each of which has his own strength.

Apr 19, 2025 • Leetcode

Detect Capital

We define the usage of capitals in a word to be right when one of the following cases holds:

Apr 19, 2025 • Codechef

CRED Coins

For each bill you pay using CRED, you earn X CRED coins. At CodeChef store, each bag is worth 100 CRED coins.

Apr 18, 2025 • HackerRank

HackerRank in a String

We say that a string contains the word hackerrank if a of its characters spell the word hackerrank. Remeber that a subsequence maintains the order of characters

Apr 18, 2025 • Codeforces

Timofey and cubes

Young Timofey has a birthday today! He got kit of n cubes as a birthday present from his parents.

Apr 18, 2025 • Codechef

Mahasena

Kattapa, as you all know was one of the greatest warriors of his time

Apr 18, 2025 • Leetcode

Binary Watch

A binary watch has 4 LEDs on the top to represent the hours (0-11), and 6 LEDs on the bottom to represent the minutes (0-59). Each LED represents a zero or one.

Apr 17, 2025 • Codechef

Chef in his Office

Recently Chef joined a new company. In this company, the employees have to work for X

Apr 17, 2025 • Codeforces

Game With Sticks

After winning gold and silver in IOI 2014, Akshat and Malvika want to have some fun. Now they are playing a game on a grid made of n horizontal and m vertical.

Apr 17, 2025 • Leetcode

Longest Palindrome

Given a string s which consists of lowercase or uppercase letters, return the length of the longest palindrome that can be built with those letters.

Apr 16, 2025 • HackerRank

Making Anagrams

We consider two strings to be anagrams of each other if the first string's letters can be rearranged to form the second string.

Apr 16, 2025 • Codeforces

Mahmoud and a Triangle

Mahmoud has n line segments, the i-th of them has length ai. Ehab challenged him to use exactly 3 line segments to form a non-degenerate triangle.

Apr 16, 2025 • Leetcode

Longest Common Prefix

Write a function to find the longest common prefix string amongst an array of strings.

Apr 15, 2025 • Codechef

Janmansh and Assignments

Janmansh has to submit 3 assignments for Chingari before 10 pm and he starts

Apr 15, 2025 • HackerRank

Frog in Maze

Alef the Frog is in an two-dimensional maze represented as a table.

Apr 15, 2025 • Codechef

Subscriptions

A new TV streaming service was recently started in Chefland called the Chef-TV.

Apr 15, 2025 • Leetcode

Repeated String Match

Given two strings a and b, return the minimum number of times you should repeat string a so that string b is a substring of it.

Apr 15, 2025 • Codeforces

Timofey and cubes

Young Timofey has a birthday today! He got kit of n cubes as a birthday present from his parents

Apr 14, 2025 • Codechef

Greater Average

Determine whether the average of A and B is strictly greater than C or not?

Apr 14, 2025 • HackerRank

Organizing Containers of Balls

David has several containers, each with a number of balls in it. He has just enough containers to sort each type of ball he has into its own container.

Apr 14, 2025 • Leetcode

Valid Parentheses

Given a string s containing just the characters '(', ')', '{', '}', '[' and ']', determine if the input string is valid.

Apr 14, 2025 • Codeforces

Neverending competitions

There are literally dozens of snooker competitions held each year, and team Jinotega

Apr 13, 2025 • Codechef

Valentine is Coming

Valentine's Day is approaching and thus Chef wants to buy some chocolates for someone special.

Apr 13, 2025 • HackerRank

Non-Divisible Subset

Given a set of distinct integers, print the size of a maximal subset of where the sum of any numbers in is not evenly divisible by k.

Apr 13, 2025 • Leetcode

Count and Say

The count-and-say sequence is a sequence of digit strings defined by the recursive formula

Apr 13, 2025 • Codeforces

A Serial Killer

Sherlock is currently trying to catch a serial killer who kills a person each day.

Apr 12, 2025 • HackerRank

Append and Delete

You have two strings of lowercase English letters. You can perform two types of operations on the first string

Apr 12, 2025 • Codeforces

Polycarp and Letters

Polycarp loves lowercase letters and dislikes uppercase ones. Once he got a string s consisting only of lowercase and uppercase Latin letters.

Apr 12, 2025 • Leetcode

Group Anagrams

Given an array of strings strs, group the anagrams together. You can return the answer in any order.

Apr 12, 2025 • Codechef

Reverse The Number

Given an Integer N, write a program to reverse it.

Apr 11, 2025 • HackerRank

Equalize the Array

Given an array of integers, determine the minimum number of elements to delete to leave only elements of equal value.

Apr 11, 2025 • Codechef

Nearest Exit

There are two exits in a bus with 100 seats

Apr 11, 2025 • Codeforces

Anton and Fairy Tale

Anton likes to listen to fairy tales, especially when Danik, Anton's best friend, tells them. Right now Danik tells Anton a fairy tale.

Apr 11, 2025 • Leetcode

Add Binary

Given two binary strings a and b, return their sum as a binary string.

Apr 11, 2025 • HackerRank

Extra Long Factorials

The factorial of the integer , written , is defined as

Apr 10, 2025 • Codeforces

Taymyr is calling you

Comrade Dujikov is busy choosing artists for Timofey's birthday and is recieving calls from Taymyr from Ilia-alpinist.

Apr 10, 2025 • Codechef

Is the Score Consistent

Chef is watching a football match. The current score is A

Apr 10, 2025 • Leetcode

Best Time to Buy and Sell Stock

You are given an array prices where prices[i] is the price of a given stock on the ith day.

Apr 10, 2025 • HackerRank

Jumping on the Clouds: Revisited

A child is playing a cloud hopping game. In this game, there are sequentially numbered clouds that can be thunderheads or cumulus clouds.

Apr 09, 2025 • Codeforces

Petya and Strings

Little Petya loves presents. His mum bought him two strings of the same size for his birthday

Apr 09, 2025 • Leetcode

Reverse Integer

Given a signed 32-bit integer x, return x with its digits reversed. If reversing x causes the value to go outside the signed 32-bit integer range.

Apr 09, 2025 • Codechef

Best of Two

Chef took an examination two times. In the first attempt, he scored XX marks while in the second attempt he scored YY marks

Apr 08, 2025 • HackerRank

Repeated String

There is a string of lowercase English letters that is repeated infinitely many times. Given an integer

Apr 08, 2025 • Codeforces

Soldier and Bananas

A soldier wants to buy w bananas in the shop. He has to pay k dollars for the first banana.

Apr 08, 2025 • Leetcode

554 Brick Wall

There is a rectangular brick wall in front of you with n rows of bricks. The ith row has some number of bricks each of the same height (i.e., one unit)

Apr 08, 2025 • Codechef

Monopoly

There is said to be a monopoly in the market if the profit made by one company is strictly greater than the sum of profits made by all other companies

Apr 08, 2025 • HackerRank

Taum and B'day

Taum is planning to celebrate the birthday of his friend, Diksha. There are two types of gifts that Diksha wants from Taum

Apr 07, 2025 • Codechef

Elections in Chefland

Election season has started in Chefland and the election commission wants to know the count of eligible voters.

Apr 07, 2025 • Leetcode

461 Hamming Distance

The Hamming distance between two integers is the number of positions at which the corresponding bits are different.

Apr 07, 2025 • Codeforces

118A String Task

There are n stones on the table in a row, each of them can be red

Apr 07, 2025 • HackerRank

Jumping on the Clouds

There is a new mobile game that starts with consecutively numbered clouds.

Apr 06, 2025 • HackerRank

Sherlock and Squares

Watson likes to challenge Sherlock's math ability. He will provide a starting and ending value that describe a range of integers.

Apr 06, 2025 • Codeforces

266B Queue at the School

During the break the schoolchildren, boys and girls, formed a queue of n people in the canteen.

Apr 06, 2025 • Leetcode

221 Maximal Square

Given an m x n binary matrix filled with 0's and 1's, find the largest square containing only 1's and return its area.

Apr 05, 2025 • Codeforces

4C Registration system

A new e-mail service "Berlandesk" is going to be opened in Berland in the near future

Apr 05, 2025 • Codechef

Difficulty 571 : Car or Bike

Chef wants to reach home as soon as possible. He has two options.

Apr 05, 2025 • Leetcode

542 Matrix

Given an m x n binary matrix mat, return the distance of the nearest 0 for each cell.

Apr 04, 2025 • Leetcode

204. Count Primes

Given an integer n, return the number of prime numbers that are strictly less than n.

Apr 04, 2025 • HackerRank

Circular Array Rotation

John Watson knows of an operation called a right circular rotation on an array of integers.

Apr 04, 2025 • Codeforces

27A Next Test

«Polygon» is a system which allows to create programming tasks in a simple and professional way.

Apr 03, 2025 • Codeforces

379A New Year Candles

Vasily the Programmer loves romance, so this year he decided to illuminate his room with candles

Apr 03, 2025 • HackerRank

Save the Prisoner

A jail has a number of prisoners and a number of treats to pass out to them

Apr 03, 2025 • Leetcode

207 Course Schedule

There are a total of numCourses courses you have to take, labeled from 0 to numCourses - 1

Apr 02, 2025 • Codeforces

478A Initial Bet

There are five people playing a game called "Generosity

Apr 02, 2025 • HackerRank

Viral Advertising

HackerLand Enterprise is adopting a new viral advertising strategy

Apr 02, 2025 • Leetcode

367 Valid Perfect Square

Given a positive integer num, return true if num is a perfect square or false otherwise.

Apr 01, 2025 • HackerRank

The Hurdle Race

A video player plays a game in which the character competes in a hurdle race.

Apr 01, 2025 • HackerRank Math

nCr table

Jim is doing his discrete maths homework which requires him to repeatedly calculate nCr(n choose r) for different values of n.

Apr 01, 2025 • Leetcode

35. Search Insert Position

Given a sorted array of distinct integers and a target value, return the index if the target is found. If not, return the index where it would be if it were.

Apr 01, 2025 • Codeforces

266A Stones on the Table

There are n stones on the table in a row, each of them can be red, green or blue

Mar 31, 2025 • Leetcode

69. Sqrt(x)

Given a non-negative integer x, return the square root of x rounded down to the nearest intege.

Mar 30, 2025 • Codeforces

112A Petya and Strings

Little Petya loves presents. His mum bought him two strings of the same size for his birthday

Mar 30, 2025 • Codeforces

427 Prison Transfer

The prison of your city has n prisoners. As the prison can't accommodate all of them, the city mayor has decided to transfer c of the prisoners to a prison.

Mar 30, 2025 • Leetcode

50. Pow(x, n)

Implement pow(x, n), which calculates x raised to the power n (i.e., xn).

Mar 29, 2025 • Codeforces

1734 Select Three Sticks

You are given n sticks with positive integral length a1,a2

Mar 29, 2025 • Codeforces

2490. Circular Sentence

A sentence is a list of words that are separated by a single space with no leading or trailing spaces

Mar 29, 2025 • HackerRank

Migratory Birds

Given an array of bird sightings where every element represents a bird type id

Mar 28, 2025 • Leetcode

62. Unique Paths

There is a robot on an m x n grid. The robot is initially located at the top-left corner.

Mar 27, 2025 • Leetcode

120. Triangle

Given a triangle array, return the minimum path sum from top to bottom

Mar 26, 2025 • Data Structures & Algorithms

Stack Data Structure

A Stack is a linear data structure that follows a particular order in which the operations are performed. The order may be LIFO(Last In First Out).

Mar 26, 2025 • Leetcode

91. Decode Ways

A message containing letters from A-Z is being encoded to numbers using the following mapping.

Mar 26, 2025 • Codeforces

1742C -Stripes

On an 8×8 grid, some horizontal rows have been painted red, and some vertical columns have been painted blue

Mar 25, 2025 • Leetcode

2. Add Two Numbers

You are given two non-empty linked lists representing two non-negative integers.

Mar 25, 2025 • Codeforces

Swap Game

Alice and Bob are playing a game on an array a of n positive integers

Mar 24, 2025 • HackerRank

Angry Professor

A Discrete Mathematics professor has a class of students. Frustrated with their lack of discipline.

Mar 24, 2025 • Leetcode

794. Valid Tic-Tac-Toe State

Given a Tic-Tac-Toe board as a string array board, return true if and only if it is possible to reach

Mar 23, 2025 • HackerRank

Divisible Sum Paris

Given an array of integers and a positive integer , determine the number of pairs where and + is divisible by .

Mar 23, 2025 • Leetcode

394. Decode String

The encoding rule is: k[encoded_string], where the encoded_string inside the square brackets is being repeated exactly k

Mar 22, 2025 • Leetcode

526. Beautiful Arrangement

Suppose you have n integers labeled 1 through n. A permutation of those n integers.

Mar 21, 2025 • Leetcode

318. Maximum Product of Word Lengths

Given a string array words, return the maximum value of length(word[i]) * length(word[j])

Mar 20, 2025 • Leetcode

239. Sliding Window Maximum

You are given an array of integers nums, there is a sliding window of size k.

Mar 19, 2025 • Data Structures & Algorithms

Binary Tree Data Structure

A Binary Tree Data Structure is a hierarchical data structure in which each node has at most two children.

Mar 19, 2025 • Codeforces

Problem - 239A Two Bags of Potatoes

Valera had two bags of potatoes, the first of these bags contains x (x ≥ 1) potatoes.

Mar 19, 2025 • Leetcode

152. Maximum Product Subarray

Given an integer array nums, find a subarray that has the largest product, and return the product.

Mar 18, 2025 • HackerRank

ACM ICPC Team

There are a number of people who will be attending ACM-ICPC World Finals.

Mar 18, 2025 • Leetcode

581. Shortest Unsorted Continuous Subarray

Given an integer array nums, you need to find one continuous subarray such that if you only sort this subarray in non-decreasing order.

Mar 18, 2025 • Codeforces

Problem - 231A

One day three best friends Petya, Vasya and Tonya decided to form a team and take part in programming contests.

Mar 17, 2025 • ICPC (International Collegiate Programming Contest)

47th ICPC World Final 2023

The 47th ICPC World Finals 2023 (International Collegiate Programming Contest) was a prestigious global programming competition where top university.

Mar 17, 2025 • Hackathon

Favourite Singer

Bob has a playlist of N songs, each song has a singer associated with it (denoted by an integer)

Mar 17, 2025 • Codeforces

Problem - 158B Taxi

After the lessons n groups of schoolchildren went outside and decided to visit Polycarpus to celebrate his birthday. We know that the i-th group consists

Mar 17, 2025 • Data Structures & Algorithms

Big O Notation

The efficiency and accuracy of algorithms have to be analysed to compare them and choose a specific algorithm for certain scenarios.

Mar 17, 2025 • HackerRank Math

Find the Point

Consider two points, and . We consider the inversion or point reflection, , of point across point to be a rotation of point around . Given sets of points

Mar 16, 2025 • HackerRank

Staircase

Its base and height are both equal to . It is drawn using # symbols and spaces. The last line is not preceded by any spaces.

Mar 16, 2025 • Leetcode

Maximize Distance to Closest Person

You are given an array representing a row of seats where seats[i] = 1 represents a person sitting in the ith seat, and seats[i] = 0 represents that the ith.

Mar 16, 2025 • Leetcode

Letter Combinations of a Phone Number Problem

Given a string containing digits from 2-9 inclusive, return all possible letter combinations that the number could represent. Return the answer in any order.

Mar 16, 2025 • Leetcode

Two Sum Problem

LeetCode Problem 1. Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

Mar 16, 2025 • HackerRank

Since 1800 is leap year as per Julian calendar. Day lies on

the year 1800 was a leap year in the Julian calendar. However, by that time, many countries had already switched to the Gregorian calendar, which did not consid