## Get the Sum of Digits / Digital Root using Java

The challenge Digital root is the recursive sum of all the digits in a number. Given n, take the sum of the digits of n. If that value has… Read More »Get the Sum of Digits / Digital Root using Java

The challenge Digital root is the recursive sum of all the digits in a number. Given n, take the sum of the digits of n. If that value has… Read More »Get the Sum of Digits / Digital Root using Java

The challenge of solving valid Sudoku blocks Determine if a 9×9 Sudoku board is valid. Only the filled cells need to be validated according to the following rules: Each… Read More »Check if Valid Sudoku Blocks in Java

The challenge Write a program that outputs the string representation of numbers from 1 to n. But for multiples of three it should output “Fizz” instead… Read More »FizzBuzz in Java

Python has a fantastic feature called slices. It allows you to work with a list, set or string by it’s index items. E.g.: You can… Read More »Python Splices reimplemented in Java

The challenge Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases. Note: For the purpose of this problem, we… Read More »Is a Valid Palindrome with Java

The challenge Given two strings s and t , write a function to determine if t is an anagram of s. Example 1: Input: s = “anagram”, t = “nagaram” Output: true… Read More »Is a Valid Anagram with Java

What we want to achieve Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack. Example 1:… Read More »How to ReImplement strStr() in Java

The challenge Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must… Read More »Third Maximum Number with Java

The challenge Given a string, find the first non-repeating character in it and return its index. If it doesn’t exist, return -1. Examples: s =… Read More »First Unique Character in a String using Java

What do you do when you create a new Maven Java project, and when you run it, you get the following error: Error:java: error: release… Read More »How to fix the Release Version 5 Not Supported error in IntelliJ

The challenge Given a 32-bit signed integer, reverse digits of an integer. Example 1: Input: 123 Output: 321 Example 2: Input: -123 Output: -321 Example… Read More »How to Reverse an Integer in Java

The challenge Write a function that reverses a string. The input string is given as an array of characters char[]. Do not allocate extra space for… Read More »Reverse a String in-place using Java

The challenge Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least… Read More »Check if a Java array Contains Duplicates

The challenge Students are asked to stand in non-decreasing order of heights for an annual photo. Return the minimum number of students that must move… Read More »The Array Height Checker Problem in Java

The challenge Given an array of integers A sorted in non-decreasing order, return an array of the squares of each number, also in sorted non-decreasing order. Example 1: Input:… Read More »Find the Squares of a Sorted Array in Java

The challenge Given an array A of non-negative integers, return an array consisting of all the even elements of A, followed by all the odd elements of A. You… Read More »Sorting a Java Array by Parity

Say you have an array of primitive integers and you want to remove all duplicates. You can find out how many non-duplicate integers are in… Read More »Remove Duplicates from Sorted Array in Java

The challenge Given an array arr, replace every element in that array with the greatest element among the elements to its right, and replace the last element with -1.… Read More »Replace Elements with Greatest Element on Right Side using Java

Introducing the problem Given an array A of integers, return true if and only if it is a valid mountain array. Recall that A is a mountain array if and… Read More »The Valid Mountain Array Problem using Java

The challenge Given an array nums of integers, return how many of them contain an even number of digits. Example 1: Input: nums = [12,345,2,6,7896] Output: 2 Explanation: 12… Read More »Find Numbers with Even Number of Digits using Java

What is a HashSet A HashSet is an unordered collection containing unique elements. It has the standard collection operations Add, Remove, Contains, but since it… Read More »How to use a Java HashSet by example

The Challenge An encoded string S is given. To find and write the decoded string to a tape, the encoded string is read one character at a time and the following… Read More »The Decoded String at Index using Java

The question Given a binary search tree with non-negative values, find the minimum absolute difference between values of any two nodes. Example: Input: 1 \ 3 /… Read More »Find the Minimum Absolute Difference in BST using Java

The problem Given an integer array nums, find the contiguous subarray (containing at least one number) which has the largest sum and return its sum. Example: Input:… Read More »Find Maximum Subarrays using Java

The problem Given a positive integer num, output its complement number. The complement strategy is to flip the bits of its binary representation. Example 1: Input: num =… Read More »Finding Number Complements using Java