Task: Sudoku Solver

Write a program (C or C#) which solves a Sudoku using a backtracking algorithm. The solution shall be printed to an output file.

Usage

./PROG SUDOKU_FILE

Example

PROMPT> cat data/s01a.txt
0 4 0 0 0 0 1 7 9 
0 0 2 0 0 8 0 5 4 
0 0 6 0 0 5 0 0 8 
0 8 0 0 7 0 9 1 0 
0 5 0 0 9 0 0 3 0 
0 1 9 0 6 0 0 4 0 
3 0 0 4 0 0 7 0 0 
5 7 0 1 0 0 2 0 0 
9 2 8 0 0 0 0 6 0 
PROMPT> ./PROG data/s01.txt
PROMPT> cat data/s01_out.txt
8 4 5 6 3 2 1 7 9
7 3 2 9 1 8 6 5 4
1 9 6 7 4 5 3 2 8
6 8 3 5 7 4 9 1 2
4 5 7 2 9 1 8 3 6
2 1 9 8 6 3 5 4 7
3 6 1 4 2 9 7 8 5
5 7 4 1 8 6 2 9 3
9 2 8 3 5 7 4 6 1