Prolog

       [7,_,_,_,4,3,_,_,_],
       [_,1,_,7,_,_,6,_,_],
       [_,4,_,_,1,_,_,_,2],
       [_,_,_,_,_,_,4,1,_],
       [_,_,7,1,_,9,5,_,_],
       [_,6,5,_,_,_,_,_,_],
       [2,_,_,_,6,_,_,8,_],
       [_,_,4,_,_,8,_,9,_],
       [_,_,_,9,2,_,_,_,6]

This application uses backtracking algorithm to solve sudoku. The sample problem given has the solution shown below. The sample problem can be run using the call:

?>herald.

7 1 2 | 5 4 3 | 6 8 9 2 1 3 | 7 4 5 | 6 8 9 3 4 5 | 6 1 7 | 8 9 2 2 3 5 | 6 7 8 | 4 1 9 2 3 7 | 1 4 9 | 5 6 8 1 6 5 | 2 3 4 | 7 8 9 2 1 3 | 4 6 5 | 7 8 9 1 2 4 | 3 5 8 | 6 9 7 1 3 4 | 9 2 5 | 7 8 6

To solve other problems using this implementation run: ?>sudoku(R1,R2,R3,R4,R5,R6,R7,R8,R9) Where Rn is the nth row of 9*9 sudoku you want to solve and Rn is a list of size 9.