alienDeveloper

Well the constraint propagation is quite good. My logic adds one more constraint.

If any of the possible values of a cell is not possible in any of the other conflicting cell than its safe to assume that, that value is the value of this cell.

hope its not confused. check the line 313 to 386 of my code.

because brute-force executes very quickly for easy sudoku's but as it gets harder and lesser values are provided it takes too much time.

this is not a brute force trick.. it calculate all possibilities and eliminate others using constraint theories.