alpha beta剪枝是一种用于优化博弈树搜索算法的技术,启发式函数可以用来估计当前局面的价值,从而在搜索中提供更好的剪枝机会。下面是一个使用alpha beta剪枝和启发式函数来解决博弈问题的示例代码:
# 启发式函数,用于评估当前局面的价值,返回一个评估值
def heuristic(board):
# 根据具体问题设计启发式函数
# 这里假设当前局面的价值为黑子数量减去白子数量
black_count = sum([1 for row in board for cell in row if cell == 'B'])
white_count = sum([1 for row in board for cell in row if cell == 'W'])
return black_count - white_count
# alpha beta剪枝函数,返回最佳行动和对应的评估值
def alpha_beta(board, depth, alpha, beta, maximizing_player):
if depth == 0 or game_over(board):
return None, heuristic(board)
if maximizing_player:
max_eval = float('-inf')
best_action = None
for action in get_possible_actions(board):
new_board = make_move(board, action)
_, eval = alpha_beta(new_board, depth - 1, alpha, beta, False)
if eval > max_eval:
max_eval = eval
best_action = action
alpha = max(alpha, eval)
if beta <= alpha:
break # beta剪枝
return best_action, max_eval
else:
min_eval = float('inf')
best_action = None
for action in get_possible_actions(board):
new_board = make_move(board, action)
_, eval = alpha_beta(new_board, depth - 1, alpha, beta, True)
if eval < min_eval:
min_eval = eval
best_action = action
beta = min(beta, eval)
if beta <= alpha:
break # alpha剪枝
return best_action, min_eval
# 在主函数中调用alpha beta剪枝函数
def main():
board = [['B', 'B', 'W'],
['W', 'B', 'W'],
['B', 'W', 'B']]
depth = 3
alpha = float('-inf')
beta = float('inf')
maximizing_player = True
best_action, eval = alpha_beta(board, depth, alpha, beta, maximizing_player)
print("Best action:", best_action)
print("Evaluation value:", eval)
if __name__ == '__main__':
main()
这个示例代码展示了如何使用alpha beta剪枝和启发式函数来解决博弈问题。其中heuristic函数用于评估当前局面的价值,alpha_beta函数使用alpha beta剪枝算法进行搜索,最后在main函数中调用alpha_beta函数来找到最佳行动和对应的评估值。