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 Linear Search

Beginner

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

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.

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.

Array Math Number Theory

Learner

Implement the `findMissingNumberFromOneToN` method that finds the missing value from a sequence that should contain numbers from 1 to n.

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.

Loop Array Decision Making

Intermediate

Implement the `findSecondLargestDistinct` method that returns the second largest distinct value from the array.

Loop Array Two Pointers

Learner

Implement the `moveZerosToEndCopy` method that returns a copy of the array with all zero values moved to the end.

Loop Array Decision Making

Learner

Implement the `isArrayStrictlyIncreasing` method that checks whether every array element is greater than the element before it.

Loop Array Two Pointers

Learner

Implement the `reverseArrayCopy` method that returns a new array with the input elements in reverse order.

Array Two Pointers

Proficient

Implement the method `trappedRainWater` that calculates how much water can be trapped between bars.

Array Dynamic Programming

Proficient

Implement the method `longestIncreasingSubsequence` that returns the length of the longest strictly increasing subsequence.

Proficient

Implement the method `minJumpsToEnd` that returns the fewest jumps needed to reach the last index.

Array Prefix Sum Dynamic Programming

Intermediate

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

Array Binary Search

Intermediate

Implement the method `searchRotatedArray` that finds a target in a rotated sorted array.

Array Counting Greedy

Intermediate

Implement the method `majorityElement` that returns the value appearing more than half the time.