Ruining Sudoku  -  A Data Science project (Part 3: Digits recognition and Sudoku solver) - sudoku_solver.py

sudoku_solver.py

def find_empty_grid(x):  # checks for empty spaces '0'.
    for i in range(len(x)):
        for j in range(len(x[0])):
            if x[i][j] == 0:
                return (i, j)  # return row, col

    return None


def solve_array(x):
    find = find_empty_grid(x)  # find the empty spaces
    if not find:
        return True
    else:
        row, col = find

    for i in range(1, 10):
        if valid(x, i, (row, col)):  # check the constraints
            x[row][col] = i

            if solve_array(x):
                return True

            x[row][col] = 0

    return False


def valid(x, num, pos):  # this function checks the constraints
    # Check row
    for i in range(len(x[0])):
        if x[pos[0]][i] == num and pos[1] != i:
            return False

    # Check column
    for i in range(len(x)):
        if x[i][pos[1]] == num and pos[0] != i:
            return False

    # Check box
    box_x = pos[1] // 3
    box_y = pos[0] // 3

    for i in range(box_y * 3, box_y * 3 + 3):
        for j in range(box_x * 3, box_x * 3 + 3):
            if x[i][j] == num and (i, j) != pos:
                return False

    return True


def print_board(x):
    """
    Print the array with a better look.
    """
    for i in range(len(x)):
        if i % 3 == 0 and i != 0:
            print("- - - - - - - - - - - - - ")

        for j in range(len(x[0])):
            if j % 3 == 0 and j != 0:
                print(" | ", end="")

            if j == 8:
                k = "." if x[i][j] == 0 else str(x[i][j])
                print(k)
            else:
                k = "." if x[i][j] == 0 else str(x[i][j])
                print(k + " ", end="")