I don't know anything, but I do know that everything is interesting if you go into it deeply enough. ~Richard Feynman

AlgorithmX Using Dancing Links

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Solving a Sudoku puzzle of every size and form has always given me a sense of happiness. I first wrote a Sudoku solver using naive backtracking (checking every possibility) with my two other friends Shreesha and Harsha back in 2007 as part of a summer project, which involved developing a C program to solve a sudoku puzzle and create a nice interface for it using graphics.h in TurboC.

Fast forward a few years I came across a paper by Prof. Donald Knuth called the Dancing Links. This paper not only provides an algorithm to efficiently solve exact cover problems but also presents a neat little data structure to speed it up.

I have been meaning to try out Dancing Links to solve the Sudoku for some time but never got around to it. So, when I was playing around with Scala and wanted to write something up using it, I decided to go ahead and implement it.

What is implemented ?

  • DLX data structure.
  • Methods DLX data structure needs to support to facilitate AlgorithmX.
  • Class to solve exact cover problems using DLX and AlgorithmX.
  • Class to solve 9x9 sudoku problems using DLX and AlgorithmX.

Where to find the code ?