[ally]

...java...

public class Sudoku {

     public static void main(String[] args) {
    	
    	args = new String[]{"153","178","185","221","242","335","357","424","461","519","605","677","683","722","741","844","889"};
    	
    	long time = System.currentTimeMillis();
    	
        int[][] matrix = parseProblem(args);
        writeMatrix(matrix);
        if (solve(0,0,matrix))    // solves in place
            writeMatrix(matrix);
        else
            System.out.println("NONE");
        
        System.out.println("in "+(System.currentTimeMillis()-time)+" millis");
    }

    static boolean solve(int i, int j, int[][] cells) {
        if (i == 9) {
            i = 0;
            if (++j == 9)
                return true;
        }
        if (cells[i][j] != 0)  // skip filled cells
            return solve(i+1,j,cells);

        for (int val = 1; val <= 9; ++val) {
            if (legal(i,j,val,cells)) {
                cells[i][j] = val;
                if (solve(i+1,j,cells))
                    return true;
            }
        }
        cells[i][j] = 0; // reset on backtrack
        return false;
    }

    static boolean legal(int i, int j, int val, int[][] cells) {
        for (int k = 0; k < 9; ++k)  // row
            if (val == cells[k][j])
                return false;

        for (int k = 0; k < 9; ++k) // col
            if (val == cells[i][k])
                return false;

        int boxRowOffset = (i / 3)*3;
        int boxColOffset = (j / 3)*3;
        for (int k = 0; k < 3; ++k) // box
            for (int m = 0; m < 3; ++m)
                if (val == cells[boxRowOffset+k][boxColOffset+m])
                    return false;

        return true; // no violations, so it's legal
    }

    static int[][] parseProblem(String[] args) {
        int[][] problem = new int[9][9]; // default 0 vals
        for (int n = 0; n < args.length; ++n) {
            int i = Integer.parseInt(args[n].substring(0,1));
            int j = Integer.parseInt(args[n].substring(1,2));
            int val = Integer.parseInt(args[n].substring(2,3));
            problem[i][j] = val;
        }
        return problem;
    }

    static void writeMatrix(int[][] solution) {
        for (int i = 0; i < 9; ++i) {
            if (i % 3 == 0)
                System.out.println(" -----------------------");
            for (int j = 0; j < 9; ++j) {
                if (j % 3 == 0) System.out.print("| ");
                System.out.print(solution[i][j] == 0
                                 ? " "
                                 : Integer.toString(solution[i][j]));

                System.out.print(' ');
            }
            System.out.println("|");
        }
        System.out.println(" -----------------------");
    }

}

 -----------------------
| 9 8 7 | 6 5 4 | 3 2 1 |
| 2 4 6 | 1 7 3 | 9 8 5 |
| 3 5 1 | 9 2 8 | 7 4 6 |
 -----------------------
| 1 2 8 | 5 3 7 | 6 9 4 |
| 6 3 4 | 8 9 2 | 1 5 7 |
| 7 9 5 | 4 6 1 | 8 3 2 |
 -----------------------
| 5 1 9 | 2 8 6 | 4 7 3 |
| 4 7 2 | 3 1 9 | 5 6 8 |
| 8 6 3 | 7 4 5 | 2 1 9 |
 -----------------------
in 41309 millis

...su centrino 1,6 Ghz prima maniera...

...ciao Andrea...