config_validity_checker.py

# __func() = Utility function


def __not_inrow(arr, row):
    st = set()

    for i in range(0, 9):

        # If already encountered before
        if arr[row][i] in st:
            return False

        # If not an empty cell, insert value at the current cell in set
        if arr[row][i] not in [" ", 0]:
            st.add(arr[row][i])

    return True


# check duplicates in column
def __not_incol(arr, col):
    st = set()

    for i in range(0, 9):

        # If already encountered before
        if arr[i][col] in st:
            return False

        # If not an empty cell, insert value at the current cell in set
        if arr[i][col] not in [" ", 0]:
            st.add(arr[i][col])

    return True


# check duplicates in 3x3 box
def __not_inbox(arr, startRow, startCol):

    st = set()

    for row in range(0, 3):
        for col in range(0, 3):
            curr = arr[row + startRow][col + startCol]

            # If already encountered before,
            # return false
            if curr in st:
                return False

            # If it is not an empty cell,
            # insert value at current cell in set
            if curr not in [" ", 0]:
                st.add(curr)

    return True


# Get validity of board, and invalidity in ROW, COL, or BOX
def __is_valid(arr, row, col):
    row_inv = not __not_inrow(arr, row)
    col_inv = not __not_incol(arr, col)
    box_inv = not __not_inbox(arr, row - row % 3, col - col % 3)

    return (row_inv, col_inv, box_inv)


def currentconfig_isvalid(board, num, pos):
    # Check row
    for i in range(len(board[0])):
        if board[pos[0]][i] == num and pos[1] != i:
            return False

    # Check column
    for i in range(len(board)):
        if board[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 board[i][j] == num and (i, j) != pos:
                return False

    return True


def fullboard_isvalid(board):
    for i in range(0, len(board)):
        for j in range(0, len(board)):
            row_inv, col_inv, box_inv = __is_valid(board, i, j)
            if row_inv or col_inv or box_inv:
                return (
                    False,  # <is config valid?>
                    row_inv,  # <invaldity in row?>
                    col_inv,  # <invaldity in column?>
                    box_inv,  # <invaldity in 3x3 box?>
                )

    return True, None, None, None


if __name__ == "__main__":
    test_validboard = [
        [0, 0, 0, 8, 0, 0, 4, 2, 0],
        [5, 0, 0, 6, 7, 0, 0, 0, 0],
        [0, 0, 0, 0, 0, 9, 0, 0, 5],
        [7, 4, 0, 1, 0, 0, 0, 0, 0],
        [0, 0, 9, 0, 3, 0, 7, 0, 0],
        [0, 0, 0, 0, 0, 7, 0, 4, 8],
        [8, 0, 0, 4, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 9, 8, 0, 0, 3],
        [0, 9, 5, 0, 0, 3, 0, 0, 0],
    ]

    test_invalidboard = [
        [0, 0, 0, 8, 0, 0, 4, 2, 0],
        [5, 0, 0, 6, 7, 0, 0, 0, 0],
        [0, 5, 0, 0, 0, 9, 0, 0, 5],
        [7, 4, 0, 1, 0, 0, 0, 0, 0],
        [0, 0, 9, 0, 3, 0, 7, 0, 0],
        [0, 0, 0, 0, 0, 7, 0, 4, 8],
        [8, 0, 0, 4, 0, 0, 0, 0, 0],
        [0, 0, 0, 0, 9, 8, 0, 0, 3],
        [0, 9, 5, 0, 0, 3, 0, 0, 0],
    ]

    test3 = [
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
        [" ", " ", " ", " ", " ", " ", " ", " ", " "],
    ]

    print(fullboard_isvalid(test_validboard))
    print(fullboard_isvalid(test_invalidboard))
    print(fullboard_isvalid(test3))
    print(test3)