Code Challenges

Get better at coding with practice problems.

Coding Challenges

Select a problem, write code, run test cases, and submit your solution.

Math Combinatorics

Intermediate

Implement the `nCrValue` method that calculates the binomial coefficient value nCr.

Math Number Theory

Learner

Implement the `isArmstrongNumber` method that checks whether a number is equal to the sum of its digits raised to the digit count.

Math Number Theory Bit Manipulation

Intermediate

Implement the `fastPowerModulo` method that calculates base raised to exponent under a given modulo efficiently.

Math Number Theory

Learner

Implement the `lcmOfTwoNumbers` method that returns the least common multiple of two numbers.

Math Number Theory

Learner

Implement the `gcdOfTwoNumbers` method that returns the greatest common divisor of two numbers.

Math Number Theory

Intermediate

Implement the `countPrimeNumbersUpToN` method that counts all prime numbers from 2 up to the given number.

Math Number Theory

Learner

Implement the `isPrimeNumber` method that checks whether the given number is prime.

String Manipulation Loop String Pattern Matching

Intermediate

Implement the `countPatternOccurrences` method that counts how many times a pattern appears inside the given text.

String Manipulation String Conversion Bit Manipulation

Learner

Implement the `binaryStringToDecimal` method that converts a binary string into its decimal integer value.

String Manipulation String Stack Simulation

Learner

Implement the `removeAdjacentDuplicates` method that removes adjacent duplicate characters using stack-style processing.

String Manipulation String Two Pointers

Learner

Implement the `isSubsequenceText` method that checks whether the smaller text appears as a subsequence inside the larger text.

String Manipulation String Counting Sliding Window

Intermediate

Implement the `longestSubstringWithoutRepeat` method that returns the length of the longest substring that has no repeated characters.

String Manipulation String Pattern Matching

Learner

Implement the `isRotationOfString` method that checks whether one string can be formed by rotating the other string.

String Manipulation String Counting Character

Learner

Implement the `removeDuplicateCharacters` method that returns the text after keeping only the first occurrence of each character.

String Manipulation String Counting Character

Intermediate

Implement the `areTextsAnagram` method that checks whether two texts contain the same characters with the same frequencies.

String Manipulation String Counting Character

Intermediate

Implement the `firstNonRepeatingCharacter` method that returns the first character in the text that appears only once.

Array Sorting Two Pointers

Learner

Implement the `mergeTwoSortedArrays` method that merges two sorted arrays into one sorted result array.

Array Hash Map Counting

Learner

Implement the `findFirstRepeatedValue` method that returns the first value that appears more than once while scanning the array.

Array Prefix Sum Sliding Window

Intermediate

Implement the `maximumSubarraySumFixedLength` method that finds the maximum sum of any contiguous subarray of length k.