狼羊菜代码

狼羊菜问题是传统的人工智能领域的一个经典问题，它的简述如下：

有一只狼、一只羊和一棵菜，它们需要一起过河。但是，小船只能装下你和另外一样东西，你必须把它们全部运到对岸。如果你不在场，狼会吃掉羊，羊会吃掉菜。请问你应该如何安排它们的顺序才能安全地过河？

这个问题可以用深度优先搜索、广度优先搜索、A*搜索等算法来解决。下面是一个简单的 Python 代码实现：

# 定义状态类
class State:
    def __init__(self, wolf, sheep, vegetable, boat):
        self.wolf = wolf  # 狼的位置
        self.sheep = sheep  # 羊的位置
        self.vegetable = vegetable  # 菜的位置
        self.boat = boat  # 船的位置

    # 定义状态比较函数
    def __eq__(self, other):
        return self.wolf == other.wolf and self.sheep == other.sheep and self.vegetable == other.vegetable and self.boat == other.boat

    # 定义状态哈希函数
    def __hash__(self):
        return hash((self.wolf, self.sheep, self.vegetable, self.boat))

    # 定义状态是否合法的函数
    def is_valid(self):
        if self.sheep == self.vegetable and self.sheep != self.boat:
            return False
        if self.wolf == self.sheep and self.wolf != self.boat:
            return False
        return True

# 定义深度优先搜索函数
def dfs(state, visited, path):
    if state not in visited:
        visited.add(state)
        if state.boat == "left" and state.is_valid():
            if state == State("right", "right", "right", "right"):
                path.append(state)
                return True
            for next_state in get_next_states(state):
                if dfs(next_state, visited, path):
                    path.append(state)
                    return True
        elif state.boat == "right" and state.is_valid():
            if state == State("left", "left", "left", "left"):
                path.append(state)
                return True
            for next_state in get_next_states(state):
                if dfs(next_state, visited, path):
                    path.append(state)
                    return True
    return False

# 定义获取下一个状态的函数
def get_next_states(state):
    next_states = []
    if state.boat == "left":
        # 狼过河
        if state.wolf == "left":
            next_state = State("right", state.sheep, state.vegetable, "right")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State("left", state.sheep, state.vegetable, "right")
            if next_state.is_valid():
                next_states.append(next_state)
        # 羊过河
        if state.sheep == "left":
            next_state = State(state.wolf, "right", state.vegetable, "right")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State(state.wolf, "left", state.vegetable, "right")
            if next_state.is_valid():
                next_states.append(next_state)
        # 菜过河
        if state.vegetable == "left":
            next_state = State(state.wolf, state.sheep, "right", "right")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State(state.wolf, state.sheep, "left", "right")
            if next_state.is_valid():
                next_states.append(next_state)
    else:
        # 狼过河
        if state.wolf == "right":
            next_state = State("left", state.sheep, state.vegetable, "left")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State("right", state.sheep, state.vegetable, "left")
            if next_state.is_valid():
                next_states.append(next_state)
        # 羊过河
        if state.sheep == "right":
            next_state = State(state.wolf, "left", state.vegetable, "left")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State(state.wolf, "right", state.vegetable, "left")
            if next_state.is_valid():
                next_states.append(next_state)
        # 菜过河
        if state.vegetable == "right":
            next_state = State(state.wolf, state.sheep, "left", "left")
            if next_state.is_valid():
                next_states.append(next_state)
        else:
            next_state = State(state.wolf, state.sheep, "right", "left")
            if next_state.is_valid():
                next_states.append(next_state)
    return next_states

# 测试
start_state = State("left", "left", "left", "left")
visited = set()
path = []
dfs(start_state, visited, path)
for state in reversed(path):
    print(state.wolf, state.sheep, state.vegetable, state.boat)

该代码实现了深度优先搜索来解决狼羊菜问题，其中包括定义状态类、状态比较函数、状态哈希函数、状态是否合法的函数、获取下一个状态的函数以及深度优先搜索函数。