This Sudoku solver written in Pascal was my Matura project in 2006 at Gymnasium Friedberg.
It's consisting of a GUI where you can generate new Sudokus, solve them and get help if you don't know further. The Sudoku generation is achieved by using Knuth's Algorith X and backtracking.
The main challenge was processing the data structure using recursive function calls. As data structure I used big arrays. This is the most pragmatic approach and not very fast because most of the fields are zeroed. A stretch goal would have been to use double-linked lists (the "dancing links" extension).
