Rotate matrix clockwise
Problem statement – Given an array of N rows and N columns (square matrix), rotate the matrix by 90° in clockwise direction. […]
Category: Array Interview Questions
Print matrix in spiral order
Problem statement – Given a 2D array (or matrix) of N rows and M columns, print it in a spiral order. Example, […]
Add one to digit array
Problem statement – Given a non-negative integer in the form of an array of digits, add one to digit array. The digits […]
First missing integer in an unsorted array
Problem statement – Given an unsorted integer array, find the first missing positive integer. Example, If A = [-1, 4, 2, 3, […]
Maximum sum contiguous sub-array
Find a contiguous sub-array whose sum is maximum. Using the dynamic programming based Kadane’s Algorithm, we can solve this in O(N) time.
Find the majority element in an array
Given an unsorted array, find the majority element. Majority element is defined as that element which occurs for more than N/2 times. If the majority element exists, there will only be one such element. We can do this in O(N) time by the Boyer–Moore majority voting algorithm.
Find pivot element in a sorted and rotated array
Problem Statement – Suppose we have a sorted array, and now we rotate it N times, find the pivot element. The pivot […]
Kth smallest element in an array
Given an unsorted array of N elements, find the kth smallest element. This can be done in O(N) time and O(1) space by the Quickselect Algorithm. The Quickselect Algorithm is a divide-and-conquer based algorithm which rearranges the array such that the kth element is the kth smallest element in the array.
Intersection of two sorted arrays
Given two sorted arrays, find the intersection (elements present in both arrays). We can do this in O(M + N) time, where M and N are lengths of arrays. What we will do here is similar to the “merging” step in merge sort.
Element in an array which appears once while other elements appear twice
Problem Statement – Given an array of numbers where all numbers appear twice except for one number which appears only once, find […]