This was something I made for fun. It is a Sudoku puzzle solver.
It keeps track of the possible numbers that could occupy each square,
tries out a number and eliminates that number as a possibility in
its row, column and three by three square. When the program reaches a point
where the puzzle is impossible, because it put in a wrong number,
it backtracks and tries a different number. The time it takes to solve
a puzzle will vary based on the specs of the computer. On my laptop
it took 216 seconds to solve the first one hundred puzzles in the
sudoku1465 text file.