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 Given two arrays, write a function to compute their intersection. Example 1: Input: nums1 = [1,2,2,1], nums2 = [2,2] Output: [2,2] Example 2:… Read More »Find the Intersection of Two Arrays in Python
The challenge Given an array, rotate the array to the right by k steps, where k is non-negative. Example 1: Input: nums = [1,2,3,4,5,6,7], k = 3 Output: [5,6,7,1,2,3,4]… Read More »Rotate an Array K Times in Python
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 an array of integers, return indices of the two numbers such that they add up to a specific target. You may assume that each… Read More »Solving Two Sum in Python
The challenge Write a function: def solution(A) that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does… Read More »Get the Next Small Integer in Python
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
Why the need to hide icons? Perhaps you have a screen-share session coming up and you want a nice clean desktop to show everyone. Also,… Read More »How to Quickly Hide all Icons on a Mac’s Desktop
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
I noticed an interesting thing with a certain visitor after posting a blog post to Facebook. The IP address that the Facebook crawler uses to… Read More »Facebook’s custom IPv6 range
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 Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all… Read More »Find All Numbers Disappeared in an Array using Python
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