Write a program that solves sudoku puzzles using backtracking.

Here is a sample grid, but make sure your program works for others too.

int grid[9][9] =
{ { 6, 0, 0, 0, 0, 3, 0, 4, 0 },
  { 0, 3, 0, 0, 0, 0, 5, 0, 9 },
  { 0, 0, 0, 0, 1, 0, 8, 0, 0 },
  { 0, 0, 0, 0, 8, 0, 9, 0, 3 },
  { 0, 6, 0, 0, 9, 0, 0, 2, 0 },
  { 1, 0, 3, 0, 5, 0, 0, 0, 0 },
  { 0, 0, 5, 0, 3, 0, 0, 0, 0 },
  { 2, 0, 4, 0, 0, 0, 0, 5, 0 },
  { 0, 8, 0, 4, 0, 0, 0, 0, 1 } };

Remember: I know how to search the web too! I want original work.

You should find that a correct program finds the solution very quickly.