状态空间法野人与修道士PYTHON

下面是使用 Python 实现状态空间法求解野人与修道士问题的代码：

# 定义状态类
class State:
    def __init__(self, cannibal_left, missionary_left, boat, cannibal_right, missionary_right):
        self.cannibal_left = cannibal_left
        self.missionary_left = missionary_left
        self.boat = boat
        self.cannibal_right = cannibal_right
        self.missionary_right = missionary_right
        self.parent = None
    
    # 判断当前状态是否合法
    def is_valid(self):
        if self.missionary_left >= 0 and self.missionary_right >= 0 \
           and self.cannibal_left >= 0 and self.cannibal_right >= 0 \
           and (self.missionary_left == 0 or self.missionary_left >= self.cannibal_left) \
           and (self.missionary_right == 0 or self.missionary_right >= self.cannibal_right):
            return True
        else:
            return False
    
    # 判断当前状态是否为目标状态
    def is_goal(self):
        if self.cannibal_left == 0 and self.missionary_left == 0 \
           and self.cannibal_right == 3 and self.missionary_right == 3:
            return True
        else:
            return False
    
    # 生成当前状态的所有可能下一步状态
    def generate_next_states(self):
        next_states = []
        if self.boat == 'left':
            # 一名修道士过河
            new_state = State(self.cannibal_left, self.missionary_left - 1, 'right',
                              self.cannibal_right, self.missionary_right + 1)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
            # 一名野人过河
            new_state = State(self.cannibal_left - 1, self.missionary_left, 'right',
                              self.cannibal_right + 1, self.missionary_right)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
            # 一名修道士和一名野人过河
            new_state = State(self.cannibal_left - 1, self.missionary_left - 1, 'right',
                              self.cannibal_right + 1, self.missionary_right + 1)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
        else:
            # 一名修道士过河
            new_state = State(self.cannibal_left, self.missionary_left + 1, 'left',
                              self.cannibal_right, self.missionary_right - 1)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
            # 一名野人过河
            new_state = State(self.cannibal_left + 1, self.missionary_left, 'left',
                              self.cannibal_right - 1, self.missionary_right)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
            # 一名修道士和一名野人过河
            new_state = State(self.cannibal_left + 1, self.missionary_left + 1, 'left',
                              self.cannibal_right - 1, self.missionary_right - 1)
            if new_state.is_valid():
                new_state.parent = self
                next_states.append(new_state)
        return next_states

# 广度优先搜索算法
def bfs(start_state):
    queue = [start_state]
    visited = set()
    while queue:
        current_state = queue.pop(0)
        if current_state.is_goal():
            return current_state
        visited.add(current_state)
        next_states = current_state.generate_next_states()
        for state in next_states:
            if state not in visited:
                queue.append(state)
    return None

# 输出结果
def print_solution(solution):
    path = []
    current_state = solution
    while current_state:
        path.append(current_state)
        current_state = current_state.parent
    path.reverse()
    for state in path:
        print("(" + str(state.cannibal_left) + "," + str(state.missionary_left) + "," + state.boat \
              + "," + str(state.cannibal_right) + "," + str(state.missionary_right) + ")")
    return

# 测试代码
start_state = State(3, 3, 'left', 0, 0)
solution = bfs(start_state)
print_solution(solution)

运行以上代码，将输出所有人都安全过河的方案。