检查Matrix中的列是否重复并执行数字切换- Sudoku - Python

def is_valid_sudoku(board):
    # 检查每一列是否有重复数字
    for col in range(9):
        nums = []
        for row in range(9):
            if board[row][col] != ".":
                if board[row][col] in nums:
                    return False
                nums.append(board[row][col])
    return True

def solve_sudoku(board):
    if not is_valid_sudoku(board):
        return False

    def backtrack(board, row, col):
        if col == 9:
            return backtrack(board, row + 1, 0)
        if row == 9:
            return True

        if board[row][col] != ".":
            return backtrack(board, row, col + 1)

        for num in range(1, 10):
            if not is_valid(board, row, col, str(num)):
                continue

            board[row][col] = str(num)
            if backtrack(board, row, col + 1):
                return True
            board[row][col] = "."

        return False

    backtrack(board, 0, 0)
    return board