TicTacToe游戏中Minimax算法的优化

问题描述

我的极小极大算法实现目前似乎非常有效。虽然现在看起来很慢。我在代码中做了一些多余的事情吗？请让我看看。玩家“X”必须最大化得分，使得状态得分为 1，玩家“O”必须最小化得分，使得得分必须为 -1。我确实相信我的终端或我的获胜者功能似乎是一种开销。

import math
from copy import deepcopy

X = "X"
O = "O"
EMPTY = None


def initial_state():
    """
    Returns starting state of the board.
    """
    return [[EMPTY,EMPTY,EMPTY],[EMPTY,EMPTY]]


def player(board):
    """
    Returns player who has the next turn on a board.
    """
    if not terminal(board):
        cnt_x = 0
        cnt_o = 0
        for i in range(3):
            for j in range(3):
                if board[i][j] == EMPTY:
                    continue
                elif board[i][j] == X:
                    cnt_x += 1
                else:
                    cnt_o += 1

        if cnt_x <= cnt_o:
            return X
        else:
            return O
    else:
        return None


def actions(board):
    """
    Returns set of all possible actions (i,j) available on the board.
    """
    moves = set()
    for i in range(3):
        for j in range(3):
            if board[i][j] == EMPTY:
                moves.add((i,j))
    return moves


def result(board,action):
    """
    Returns the board that results from making move (i,j) on the board.
    """
    x = action[0]
    y = action[1]
    if x < 0 or x > 2 or y < 0 or y > 2 or not board[x][y] == EMPTY:
        raise ValueError
    temp_board = deepcopy(board)
    temp_board[x][y] = player(board)
    return temp_board


def winner(board):
    """
    Returns the winner of the game,if there is one.
    """
    chances = [X,O]
    for chance in chances:
        for row in range(3):
            if list(chance)*3 == board[row]:
                return chance
        for column in range(3):
            if [[chance] for i in range(3)] == [[board[row][column]] for row in range(3)]:
                return chance
        if board[0][0] == chance and board[1][1] == chance and board[2][2] == chance:
            return chance
        if board[0][2] == chance and board[1][1] == chance and board[2][0] == chance:
            return chance
    return None


def terminal(board):
    """
    Returns True if game is over,False otherwise.
    """

    if winner(board) is not None or (not any(EMPTY in sublist for sublist in board) and winner(board) is None):
        return True
    else:
        return False


def utility(board):
    """
    Returns 1 if X has won the game,-1 if O has won,0 otherwise.
    """
    final = winner(board)
    if final == X:
        return 1
    elif final == O:
        return -1
    else:
        return 0


def min_target(board):
    """
    Returns min_score for each board state recursively reached.
    """
    if terminal(board):
        return utility(board)
    val = math.inf
    for action in actions(board):
        val = min(val,max_target(result(board,action)))
    return val


def max_target(board):
    """
    Returns max_score for each board state recursively reached.
    """
    if terminal(board):
        return utility(board)

    val = -math.inf
    for action in actions(board):
        val = max(val,min_target(result(board,action)))
    return val


def minimax(board):
    """
    Returns the optimal action for the current player on the board.
    """
    if terminal(board):
        return utility(board)

    chance = player(board)
    if chance == X:
        v = -math.inf
        best_action = None

        for action in actions(board):
            v_temp = min_target(result(board,action))
            if v_temp > v:
                best_action = action
                v = v_temp

    else:
        v = math.inf
        best_action = None

        for action in actions(board):
            v_temp = max_target(result(board,action))
            if v_temp < v:
                best_action = action
                v = v_temp

    return best_action

解决方法

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