Today we are going to take a look at a fairly common interview question! How to Rotate a 2D Matrix by 90 Degrees in Java has a lot to do with basic linear algebra / geometry. Basically we are asked to rotate a rectangular object...

## How to Find Duplicate Number From Continuous Array

How to Find Duplicate Number From Continuous Array? I got asked this very question a long time ago at an on-site interview. It is supposed to be one of the easier questions, but I can see how certain nuances of it can become hard. First...

## How To Count Numbers Having Unique Digits In Java

How To Count Numbers Having Unique Digits In Java? This is a fairly simple looking question that gets used a lot in interviews. But although it looks simple, it has quite a bit of maths involved. We are going to take a look at a...

## Find Intersection Point of 2 Linked Lists in Java

Today we will take a look at a simple question I was asked some years ago when interviewing for an internship! The question is called “Find Intersection Point of 2 Linked Lists in Java”. Basically, we will try to write a program that takes two...

## Check if a binary tree is a BST in Java

This is a question that comes quite often as a preliminary / phone interview question. How do we check if a binary tree is a BST in Java? In other words we need to validate if a binary tree is a binary search tree. As...

## Find repeated 10 char sequences in DNA sample

FindĀ repeated 10 char sequences in DNA sampleĀ is just a modified version of Find all repeated substrings of size K, which is a pretty common question that gets asked in interviews. Since I did not find appropriate information about this question online, I decided to take...

## Merge Multiple Sorted Lists of Strings in Java

How would you Merge Multiple Sorted Lists of Strings into one list? I got asked this very question in an interview myself. And to my surprise I was not very sharp on it. The question is about developing an algorithm to find how to merge...

## Zig Zag Tree Traversal in Java

Write a method to find the zig zag tree traversal in a tree. I got asked this question once in an interview. Now I found a few solutions to this problem over the internet, but none was really explaining how to get to the solution,...

## Generate All Permutations of an Array or String in Java

How to generate all permutations of an array or string? This is quite the popular question in interviews… In fact, I personally got asked to generate all permutations of an array or string in 3 interviews last year. Therefore it is essential that if you...

## Remove duplicates from a LinkedList in PHP

The question we are going to take a look at today is how to remove duplicates from a LinkedList. We’re going to be using PHP for the coding part, just because it’s the language I use more these days. Remember, languages don’t matter as much...