THE CODE NOTE

I've never been great at solving Sudoku because I find it boring to sit down for an hour staring at boxes some filled and others to be filled with numbers. But I think it's an interesting game. I've always thought of developing an algorithm to solve any given Sudoku puzzle. I've had this in my mind from the very first year of my under graduation but I never gave it a serious thought. If you have seen my previous post, it's about backtracking which is a general algorithm used to solve many problems such as the classical N-Queens problem(I've solved it in that post). Yesterday I tried solving a question on the Hackerrank site which required me to use the backtracking algorithm and I was successful in devising an algorithm to solve it. I felt the question was very similar to solving a Sudoku puzzle so I thought of creating a sudoku solver and I've done it! It was simpler than what I thought it would be. All you need to know is how to use backtracking

This post serves as a good introduction to the backtracking method which is used widely in various types of problems to find a possible solution. Here we'll be seeing how to solve the classical N-Queens problem using backtracking method. Backtracking : The Wikipedia page  for Backtracking defines it as "a general algorithm in which, we try to incrementally build candidates to the solutions, and discard a candidate as soon as we get to know that the candidate cannot possibly be completed to a valid solution".  If that sounds complicated and confusing, don't worry! Let us understand it by running through a small example. Consider you are trapped in a haunted house with five rooms named A, B, C, D and E. Initially, you are in room A and you need to reach room E to exit the house. Below is an image of the rooms in the house. The arrows in the image indicate the directions in which you can move. For example, you can move to rooms B and C from A but, you