首选爬山法八皇后问题python代码

以下是首选爬山法解决八皇后问题的Python代码：

import random

def conflict(state, nextX):
    nextY = len(state)
    for i in range(nextY):
        if abs(state[i]-nextX) in (0, nextY-i):
            return True
    return False

def queens(num=8, state=()):
    if len(state) == num-1:
        for pos in range(num):
            if not conflict(state, pos):
                yield (pos,)
    else:
        for pos in range(num):
            if not conflict(state, pos):
                for result in queens(num, state+(pos,)):
                    yield (pos,) + result

def hill_climbing(problem):
    current = problem.initial
    while True:
        neighbor = max(problem.neighbors(current), key=problem.value)
        if problem.value(neighbor) <= problem.value(current):
            return current
        current = neighbor

class EightQueensProblem:
    def __init__(self, num=8):
        self.num = num
        self.initial = tuple(random.randint(0, num-1) for _ in range(num))

    def value(self, state):
        conflicts = 0
        for i in range(len(state)):
            for j in range(i+1, len(state)):
                if state[i] == state[j] or abs(state[i]-state[j]) == j-i:
                    conflicts += 1
        return -conflicts

    def neighbors(self, state):
        neighbors = []
        for i in range(self.num):
            if state[i] != 0:
                neighbors.append(state[:i]+(state[i]-1,)+state[i+1:])
            if state[i] != self.num-1:
                neighbors.append(state[:i]+(state[i]+1,)+state[i+1:])
        return neighbors

if __name__ == '__main__':
    problem = EightQueensProblem()
    solution = hill_climbing(problem)
    print(solution)

该代码使用了Python的生成器和类，实现了首选爬山法解决八皇后问题。其中，`conflict`函数用于判断是否有冲突，`queens`函数用于生成所有可能的解，`hill_climbing`函数用于实现首选爬山法，`EightQueensProblem`类用于表示八皇后问题，并实现了问题的初始状态、价值函数和邻居函数。最后，程序输出了一个解。