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

String Counting

Intermediate

Implement the method `compressRuns` that compresses consecutive repeated characters.

String Manipulation String

Intermediate

Implement the method `reverseWords` that reverses the order of words in a string.

Intermediate

Implement the method `isBalancedBrackets` that checks whether brackets are correctly nested.

String Manipulation String

Intermediate

Implement the method `longestCommonPrefix` that returns the shared starting text of all strings.

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.

Array Hash Map Counting

Intermediate

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

Number Theory Bit Manipulation

Learner

Implement the method `isPowerOfTwo` that checks whether an integer is a power of two.

Learner

Implement the method `productSign` that returns the sign of the product of an integer array.

Array Sorting Binary Search

Learner

Implement the method `firstOccurrence` that returns the first index of a target value in a sorted array.

Loop Array Counting

Beginner

Implement the method `countEvenNumbers` that returns how many even numbers are in an array.

String Hash Map Character

Intermediate

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

Math Conversion

Beginner

Implement the method `celsiusToFahrenheit` that converts Celsius to Fahrenheit.

Loop String Counting

Learner

Implement the method `countConsonants` that returns the number of consonants in a string.

Beginner

Implement the method `sumOfSquares` that returns the sum of squares from 1 to n.

Learner

Implement the method `fibonacci` that returns the nth Fibonacci number.

Decision Making Number Theory

Learner

Implement the method `isPrime` that checks whether an integer is prime.

Math Number Theory

Learner

Implement the method `gcd` that returns the greatest common divisor of two integers.

String Counting

Beginner

Implement the method `countWords` that returns the number of words in a string.