sudokusolver.py

def print_sudoku(sudoku):
    for row in sudoku:
        print(" ".join(map(str, row)))

def is_valid_move(sudoku, row, col, num):
    # Check if the number is not in the current row or column
    for i in range(9):
        if sudoku[row][i] == num or sudoku[i][col] == num:
            return False

    # Check if the number is not in the current 3x3 grid
    start_row, start_col = 3 * (row // 3), 3 * (col // 3)
    for i in range(3):
        for j in range(3):
            if sudoku[i + start_row][j + start_col] == num:
                return False

    return True

def solve_sudoku(sudoku):
    for row in range(9):
        for col in range(9):
            if sudoku[row][col] == 0:
                for num in range(1, 10):
                    if is_valid_move(sudoku, row, col, num):
                        sudoku[row][col] = num
                        if solve_sudoku(sudoku):
                            return True
                        sudoku[row][col] = 0  # If the move didn't lead to a solution, backtrack
                return False
    return True

# Example Sudoku puzzle as a 2D list (0 represents empty cells)
sudoku_grid = [
    [5, 3, 0, 0, 7, 0, 0, 0, 0],
    [6, 0, 0, 1, 9, 5, 0, 0, 0],
    [0, 9, 8, 0, 0, 0, 0, 6, 0],
    [8, 0, 0, 0, 6, 0, 0, 0, 3],
    [4, 0, 0, 8, 0, 3, 0, 0, 1],
    [7, 0, 0, 0, 2, 0, 0, 0, 6],
    [0, 6, 0, 0, 0, 0, 2, 8, 0],
    [0, 0, 0, 4, 1, 9, 0, 0, 5],
    [0, 0, 0, 0, 8, 0, 0, 7, 9]
]

if solve_sudoku(sudoku_grid):
    print("Solved Sudoku:")
    print_sudoku(sudoku_grid)
else:
    print("No solution exists for Sudoku.")