Programming, Sudoku, Python3, Backtracking, Search.
1: Initialization We use (i,j) to denote the position of a grid. It correspond position i in row_state[i], and j in col_state[j], and block_state[i//3)][ j//3] for corresponding sub-grid. The code is shown in function init at line 7–22. Step 2: Backtracking and Search Pruning Now, we iterate the