Code Challenges

Get better at coding with practice problems.

Coding Challenges

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

Start with beginner challenges

Loop Array Hash Map Counting Prefix Sum

Intermediate

Implement the `nextPermutationRankChange` method that returns the next lexicographical permutation of the array.

Loop Array Hash Map Counting Prefix Sum

Learner

Implement the `maximumConsecutiveOnes` method that returns the longest run of consecutive 1 values.

Loop Array Hash Map Counting Prefix Sum

Intermediate

Implement the `mergeOverlappingIntervalsCount` method that returns how many intervals remain after merging all overlaps.

Loop Array Hash Map Counting Prefix Sum

Learner

Implement the `missingNumberZeroToN` method that finds the missing number from the range 0 to n.

Loop Array Hash Map Counting Prefix Sum

Learner

Implement the `findDuplicateNumber` method that returns a duplicate value from the array.

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.

Loop Array Sorting

Learner

Implement the `insertionSortArray` method that returns the array after sorting it using insertion sort logic.

Loop Array Sorting

Learner

Implement the `bubbleSortArray` method that returns the array after sorting it using bubble sort logic.

Loop Array Sorting

Learner

Implement the `selectionSortArray` method that returns the array after sorting it using selection sort logic.

Loop Array Sorting

Learner

Implement the `isArraySortedAscending` method that checks whether the array is sorted in ascending order.

Loop Array Linear Search

Learner

Implement the `lastIndexOfTarget` method that returns the last index where the target value appears.

Loop Array Linear Search

Beginner

Implement the `linearSearchIndex` method that returns the first index of the target using linear search.

String Manipulation Loop String Pattern Matching

Intermediate

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

Learner

Implement the `rightRotateArrayByOne` method that returns the array after rotating all elements one position to the right.

Learner

Implement the `leftRotateArrayByOne` method that returns the array after rotating all elements one position to the left.