Given an array of integers, find the elements that appear twice. The main challenge of this problem is to solve it without using any extra space. You need to find a way to mark the elements that are already encountered. Once such way would be to make the elements negative. This post gives you 2 different solutions a video explanation.
Puzzle


Question: Given an array of integers, find the number of pairs of array elements that have a difference equal to the target value. Example: Input:arr[ ] = {1, 2, 3, 4}k = 1 Output: 3 Problem Statement Let us try to simplify the problem statement first and understand the sample test case. You are given an array of unique integers which is in any random order. Along with the array, you are also given a target value k. If you pick up any 2 integers from the array, they would…

Question: You are required to find missing numbers that are left out while an artist transports numbers from one array to other. The output array should be sorted. Input:arr [ ] = {7, 2, 5, 3, 5, 3}brr [ ] = {7, 2, 5, 4, 6, 3, 5, 3} Output:Missing numbers: {4, 6} Problem Statement: Let me try to simplify the problem a little first. The problem description is quite verbose and we narrow down it to quite an extent. To summarize, the artist has an original array brr, and…

Question: You are given an array of integers. After a left rotation of k times, find the resultant array. Example 1:Input: arr [ ] = {1, 2, 3, 4, 5}, size = 5, k = 2Output: {3, 4, 5, 1, 2} Example 2:Input: arr [ ] = {4, 8, 15, 16, 23, 42}, size = 6, k = 12Output: {4, 8, 15, 16, 23, 42} Terminology: To understand rotation of an array, you can assume that the array is kind of on an infinite conveyor belt, that keeps on looping.…

Brute force method would probably be the favorite algorithmic paradigm of every developer. The beauty of a brute force method is that it is pretty straightforward and if a solution to a problem exists, you are guaranteed to find it. This option is also the most exhaustive option as we might go through all the possibilities before arriving at the result. What is Brute Force Method? You might have heard the phrase “Brute force method to solve the problem”. What exactly do you mean by that? It simply means that…

Given two strings str1 and str2. Write a function to determine if str1 is an anagram of str2. Example 1:str1 = “listen”, str2 = “silent”Output = True Example 2:str1 = “mississippi”, str2 = “mips”Output = False Terminology: Anagram: Two words or phrases are said to be anagrams of each other if they can be formed by reshuffling of characters in one of them. Problem Statement: In the given problem we have 2 strings as input. They may be single words or phrases. Return true if they anagrams of each other,…

Let us suppose you are given an array of integers. The special thing about this array is that all numbers are repeated twice except one. Find the single nonrepeating number. Example 1:Input: [2, 1, 1]Output: 2 Example 2:Input: [4, 5, 5, 2, 2]Output: 4 Problem statement: You are given an array of all positive integers. All the integers are repeated exactly twice except one. We need to find that number with a linear time complexity and using the minimum space possible. Brute Force Method: When tackling such problems, it is…

Question: Let us suppose we have a two dimensional plane where the the length of lines determine the height of a container. We need to determine the maximum capacity of water this kind of an arrangement can hold. The heights are represented by an array. Input: [1, 8, 6, 2, 5, 4, 8, 3, 7] Output: 49 Let us try to visualize the problem at hand diagrammatically. Let the array be represented as: If we try to pour water from the top in the entire arrangement you can visualize that…

Question: Given an integer N, find the prime numbers in that range from 1 to N. Input: N = 25Output: 2, 3, 5, 7, 11, 13, 17, 19, 23 We have several ways of finding prime numbers. Some of the methods are discussed in the these posts. Method 1 Method 2 Method 3 In this post we will find the first N prime numbers using the Sieve of Eratosthenes. This technique is helpful in scenarios when we have to give immediate results and we need to query the prime numbers…

Question: Find the sum of even fibonacci numbers upto a limit N. Input:100Output: 44 Fibonacci numbers are a miracle of Math and are defined as: Thus the Fibonacci series can be given as0, 1, 1, 2, 3, 5, 8, 13, 21… Let us try to understand the question. We need to find all the Fibonacci numbers till a limit ‘N’ and then sum only the even numbers in them.Example:N = 10 Fibonacci numbers: 0, 1, 1, 2, 3, 5, 8 Sum of even numbers: 2 + 8 = 10 N…