We all know about the popular Sudoku game, wherein we need to arrange numbers from 1-9 such that they appear only once in a row and column of a 9x9 grid. The program uses the concept of backtracking. In this program, we have hard-coded the initial values, but you can also get the same input from the user (though that will be cumbersome for this program). The main thing to understand is the backtracking to find rows and columns that are not assigned any values (are zero).