Code Challenges

Get better at coding with practice problems.

Coding Challenges

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

Array String Hash Map Sliding Window

Intermediate

Implement the `permutationInStringCheck` method that checks whether the text contains any permutation of the pattern.

Array String Hash Map Sliding Window

Learner

Implement the `maximumAverageSubarrayFloor` method that returns the floor of the maximum average of a fixed-length subarray.

Array String Hash Map Sliding Window

Intermediate

Implement the `minimumSizeSubarraySum` method that returns the smallest subarray length whose sum reaches the target.

Array String Hash Map Sliding Window

Intermediate

Implement the `longestSubstringWithKDistinct` method that returns the longest substring length with at most k distinct characters.

Array Sorting Two Pointers

Intermediate

Implement the `boatsToSavePeopleCount` method that returns the minimum boats needed under the weight limit.

Array Sorting Two Pointers

Learner

Implement the `sortedSquaresTwoPointers` method that returns squares of sorted values in sorted order.

Array Sorting Two Pointers

Learner

Implement the `mergeSortedArrayInPlaceResult` method that merges two sorted arrays into a sorted result.

Array Sorting Two Pointers

Intermediate

Implement the `fourSumPairCountSimple` method that counts quadruplets that produce the target sum.

Array Sorting Two Pointers

Learner

Implement the `minimumDifferencePairSorted` method that returns the smallest difference between any pair after sorting.

Array Sorting Two Pointers

Learner

Implement the `validPalindromeAfterOneRemoval` method that checks whether a text can become a palindrome after removing at most one character.

Array Sorting Two Pointers

Proficient

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

Array Sorting Two Pointers

Learner

Implement the `removeDuplicatesSortedArrayLength` method that returns the length after removing duplicates from a sorted array.

Array Sorting Two Pointers

Proficient

Implement the `threeSumTripletCount` method that counts unique triplets whose sum is zero.

Array Sorting Two Pointers

Intermediate

Implement the `containerWithMostWaterArea` method that returns the maximum water area formed by two vertical lines.

Array Hash Map Counting

Intermediate

Implement the `longestSubarrayZeroSumLength` method that returns the length of the longest subarray with sum zero.

Array Hash Map Counting

Intermediate

Implement the `minimumIndexSumCommonString` method that returns the common string with the smallest index sum.

Array Hash Map Counting

Intermediate

Implement the `findAllDuplicatesCount` method that counts duplicate values found in the array.

Array Hash Map Counting

Intermediate

Implement the `validSudokuRowsSimple` method that checks whether each row of a Sudoku board is valid.

Array Hash Map Counting

Intermediate

Implement the `topKFrequentValuesCount` method that counts how many values belong to the top k frequent values.