数独を解く

sudoku.py

import math

def main(board):
    helper(board, 0, 0)
    
    return board
    
def helper(board, row, column):
    if len(board[row]) == column:
        column = 0

        row += 1

        if row == len(board):
            return True

    if board[row][column] != ".":
        return helper(board, row, column + 1)
    
    for value in range(1, 10):
        if canPlace(board, row, column, str(value)):
            board[row][column] = str(value)
            if helper(board, row, column + 1):
                return True
            board[row][column] = "."
    return False

def canPlace(board, row, column, value):
    if board[row][column] != ".":
        return False

    for b in board:
        if b[column] == value:
            return False
    for r in board[row]:
        if r == value:
            return False
    particleRow = math.floor(row / 3) * 3
    particleColumn = math.floor(column / 3) * 3
    for r in range(particleRow, particleRow + 3):
        for c in range(particleColumn, particleColumn + 3):
            if board[r][c] == value:
                return False
    return True


print(main(
[
    [".",".","5","7",".",".",".","9","."],
    [".",".",".",".",".","1",".","8","."],
    ["3",".",".",".","8",".",".",".","6"],
    [".","2",".","5",".",".",".",".","."],
    [".","3",".",".","2",".",".",".","."],
    ["6","4",".",".",".",".",".","7","."],
    ["4","9",".",".",".",".",".",".","3"],
    [".",".","8",".",".","9",".","5","."],
    [".",".",".",".",".",".","1",".","."]
]
))