Write a program that reads in an unsolved sudoku puzzle and prints the solved puzzle.
Unsolved locations in the puzzle are represented by _.
The input may be read in from a file or STDIN (your choice).
Your program should print the solved puzzle in the same format but with the _ empty slots filled in.
Example input:
1 _ 3 _ _ 6 _ 8 _
_ 5 _ _ 8 _ 1 2 _
7 _ 9 1 _ 3 _ 5 6
_ 3 _ _ 6 7 _ 9 _
5 _ 7 8 _ _ _ 3 _
8 _ 1 _ 3 _ 5 _ 7
_ 4 _ _ 7 8 _ 1 _
6 _ 8 _ _ 2 _ 4 _
_ 1 2 _ 4 5 _ 7 8
Example solution:
1 2 3 4 5 6 7 8 9
4 5 6 7 8 9 1 2 3
7 8 9 1 2 3 4 5 6
2 3 4 5 6 7 8 9 1
5 6 7 8 9 1 2 3 4
8 9 1 2 3 4 5 6 7
3 4 5 6 7 8 9 1 2
6 7 8 9 1 2 3 4 5
9 1 2 3 4 5 6 7 8
This is a problem that can be solved using exhaustive brute force or more sophisticated rules and data handling. How you go about it is up to you! :-)
This challenge is shamelessly stolen from a similar challenge in the Go community.