IndexError:索引9超出了大小为9的轴0的边界。编码数独求解器时出错

def solve_sudoku(board):
    # 检查数独是否已经解决
    if is_sudoku_solved(board):
        return board

    # 遍历数独的每个格子
    for row in range(9):
        for col in range(9):
            # 当前格子为空
            if board[row][col] == 0:
                # 尝试填入数字1到9
                for num in range(1, 10):
                    # 检查数字是否合法
                    if is_valid_move(board, row, col, num):
                        # 填入数字
                        board[row][col] = num

                        # 递归求解剩下的数独
                        result = solve_sudoku(board)
                        if result is not None:
                            return result

                        # 撤销填入的数字
                        board[row][col] = 0

    # 数独无解
    return None

def is_sudoku_solved(board):
    # 检查数独是否已经解决
    # 实现略

def is_valid_move(board, row, col, num):
    # 检查填入的数字是否合法
    # 实现略

# 使用数独求解器解决给定的数独问题
board = [
    [5, 3, 0, 0, 7, 0, 0, 0, 0],
    [6, 0, 0, 1, 9, 5, 0, 0, 0],
    [0, 9, 8, 0, 0, 0, 0, 6, 0],
    [8, 0, 0, 0, 6, 0, 0, 0, 3],
    [4, 0, 0, 8, 0, 3, 0, 0, 1],
    [7, 0, 0, 0, 2, 0, 0, 0, 6],
    [0, 6, 0, 0, 0, 0, 2, 8, 0],
    [0, 0, 0, 4, 1, 9, 0, 0, 5],
    [0, 0, 0, 0, 8, 0, 0, 7, 9]
]

result = solve_sudoku(board)
print(result)