确定Tic Tac Toe游戏结束时间的算法

def check_winner(board):
    # 检查横向
    for row in board:
        if row[0] == row[1] == row[2] and row[0] != ' ':
            return row[0]
    
    # 检查纵向
    for col in range(3):
        if board[0][col] == board[1][col] == board[2][col] and board[0][col] != ' ':
            return board[0][col]
    
    # 检查对角线
    if board[0][0] == board[1][1] == board[2][2] and board[0][0] != ' ':
        return board[0][0]
    if board[0][2] == board[1][1] == board[2][0] and board[0][2] != ' ':
        return board[0][2]
    
    return None

def is_game_over(board):
    winner = check_winner(board)
    if winner:
        return True, f"Player {winner} wins!"
    
    if all(cell != ' ' for row in board for cell in row):
        return True, "It's a draw!"
    
    return False, ""