判断数独板卡是否有效

def is_valid_sudoku(board):
    # 验证每一行
    for row in board:
        if not is_valid_row(row):
            return False
    
    # 验证每一列
    for col in range(9):
        column = [board[row][col] for row in range(9)]
        if not is_valid_row(column):
            return False
    
    # 验证每一个小九宫格
    for i in range(0, 9, 3):
        for j in range(0, 9, 3):
            square = [board[row][col] for row in range(i, i+3) for col in range(j, j+3)]
            if not is_valid_row(square):
                return False
    
    return True

def is_valid_row(row):
    seen = [False] * 9
    for num in row:
        if num != '.':
            index = int(num) - 1
            if seen[index]:
                return False
            seen[index] = True
    return True

# 测试代码
board = [
    ["5","3",".",".","7",".",".",".","."],
    ["6",".",".","1","9","5",".",".","."],
    [".","9","8",".",".",".",".","6","."],
    ["8",".",".",".","6",".",".",".","3"],
    ["4",".",".","8",".","3",".",".","1"],
    ["7",".",".",".","2",".",".",".","6"],
    [".","6",".",".",".",".","2","8","."],
    [".",".",".","4","1","9",".",".","5"],
    [".",".",".",".","8",".",".","7","9"]
]

print(is_valid_sudoku(board))  # 输出 True