Code Challenges

Get better at coding with practice problems.

Coding Challenges

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

Loop Array Hash Map Counting Prefix Sum

Intermediate

Implement the `rotateArrayRightK` method that returns the array after rotating it k positions to the right.

Loop Array Hash Map Counting Prefix Sum

Intermediate

Implement the `productArrayExceptSelf` method that returns an array where each value is the product of all other values.

Loop Array Hash Map Counting Prefix Sum

Learner

Implement the `majorityElementValue` method that returns the value that appears more than half of the time.

Loop Array Hash Map Counting Prefix Sum

Intermediate

Implement the `maximumSubarraySum` method that returns the largest sum of any contiguous subarray.

Loop Array Hash Map Counting Prefix Sum

Learner

Implement the `findTwoSumIndices` method that returns indices of two numbers whose sum equals the target.

Array Hash Map Sorting

Intermediate

Implement the `minimumSwapsToSortSmallArray` method that returns the minimum number of swaps needed to sort the array.

Array Hash Map Counting Sorting

Intermediate

Implement the `sortByFrequencyAscending` method that sorts values by increasing frequency while resolving ties consistently.

Array Hash Map Counting

Learner

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

Array Hash Map Counting

Learner

Implement the `countDistinctValues` method that counts how many different values are present in the array.

Array Hash Map Two Pointers

Intermediate

Implement the `hasPairWithExactDifference` method that checks whether any two values in the array have the required absolute difference.

String Hash Map Sliding Window

Guru

Implement the method `minimumWindowLength` that returns the length of the smallest substring containing all required characters.

String Hash Map Sliding Window

Proficient

Implement the method `longestUniqueSubstring` that returns the length of the longest substring without repeated characters.

Array Hash Map Counting

Intermediate

Implement the method `countPairsWithSum` that counts index pairs whose values add up to a target.

String Hash Map Character

Intermediate

Implement the method `firstNonRepeatingChar` that returns the first non-repeating character in a string.

String Manipulation Hash Map

Intermediate

Implement the method `isAnagram` that takes two strings and returns `true` if they are anagrams of each other, otherwise returns `false`.