The challenge Replace all vowel to exclamation mark in the sentence. aeiouAEIOU is vowel. Examples The solution in Java code We could use a StringBuilder and a… Read More »How to Replace all Vowels in a String in Java

The challenge You are given an array with positive numbers and a number N. You should find the N-th power of the element in the… Read More »How to Get the N-th Power in Java

The challenge Given a binary tree, find its minimum depth. The minimum depth is the number of nodes along the shortest path from the root… Read More »How to Count the Minimum Depth of a Binary Tree in Java

The challenge You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses… Read More »How to Solve the House Robber II Challenge in Java

The challenge Given a reference of a node in a connected undirected graph. Return a deep copy (clone) of the graph. Each node in the graph contains a val… Read More »How to Clone a Graph in Java

The challenge Ghost objects are instantiated without any arguments. Ghost objects are given a random color attribute of white” or “yellow” or “purple” or “red”… Read More »How to Return Random Values in Java

The challenge Compare two version numbers version1 and version2.If version1 > version2 return 1; if version1 < version2 return -1;otherwise return 0. You may assume that the version strings are non-empty and contain only digits and the . character. The . character does not… Read More »How to Compare Version Numbers in Java

The challenge Create a method take that accepts a list/array and a number n, and returns a list/array array of the first n elements from the list/array. If you need… Read More »How to Return the First N Elements in Java

The challenge Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row… Read More »How to Search a 2d Matrix/Array in Java

The challenge Write a function that returns the total surface area and volume of a box as an array: [area, volume] The solution in Java We… Read More »Calculate the Surface Area and Volume of a Box with Java

The challenge Complete the function which takes two arguments and returns all numbers which are divisible by the given divisor. First argument is an array… Read More »Find Numbers which are Divisible by given Number in Java

The challenge Given a non-empty array of numbers, a0, a1, a2, … , an-1, where 0 ≤ ai < 231. Find the maximum result of ai XOR aj, where… Read More »Get the Maximum XOR of Two Numbers in an Array in Java

The challenge Given a number, find its opposite. Examples: The solution in Java We return the number itself multiplied by a negative 1. This can… Read More »How to Get the Opposite of a Number in Java

The challenge You are given the length and width of a 4-sided polygon. The polygon can either be a rectangle or a square.If it is a square, return its… Read More »How to Find the Area or Perimeter of a 4-sided Polygon using Java

The challenge We take in a String where the first place contains a number, write a function that takes in this String and returns an… Read More »How to Parse Int from Char in Java

The challenge Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1. Example 1: Input:… Read More »How to Search a Binary Tree in Java

The challenge Given a linked list, rotate the list to the right by k places, where k is non-negative. Example 1: Input: 1->2->3->4->5->NULL, k = 2 Output: 4->5->1->2->3->NULL Explanation: rotate… Read More »How to Rotate a Singly Linked List in Java

The challenge You are given the root node of a binary search tree (BST) and a value to insert into the tree. Return the root node of the BST after… Read More »How to Insert into a Binary Search Tree using Java

The challenge Every non-negative integer N has a binary representation.  For example, 5 can be represented as “101” in binary, 11 as “1011” in binary, and so on.  Note that except for N = 0, there… Read More »Find the Complement of Base 10 Integer in Java

The challenge You have a RecentCounter class which counts the number of recent requests within a certain time frame. Implement the RecentCounter class: RecentCounter() Initializes the counter with zero recent… Read More »Solve the Number of Recent Calls Challenge in Java

The challenge Write a program that finds the summation of every number from 1 to num. The number will always be a positive integer greater… Read More »How to Calculate the Summation of a Number in Java

The challenge Given an array of distinct integers candidates and a target integer target, return a list of all unique combinations of candidates where the chosen numbers sum to target. You may return the combinations in any order.… Read More »How to Calculate all Unique Combinations of a Target using Backtracking in Java