Python之栈和队列

class Stack:
    def __init__(self):
        self.__list = []
    def push(self, val) -> bool:
        self.__list.append(val)
    def pop(self) -> int:
        if self.empty():
            return -1
        return self.__list.pop()
    def top(self) -> int:
        if self.empty():
            return -1
        return self.__list[-1]
    def size(self) -> int:
        return len(self.__list)
    def empty(self) -> bool:
        return self.size() == 0

class Queue:
    def __init__(self):
        self.__list = []
    # 尾入队
    def push_back(self, val):
        self.__list.append(val)
    # 头入队    
    def push_front(self, val):
        self.__list.insert(0, val) 
    # 尾出队    
    def pop_back(self) -> int:
        if self.empty():
            return -1
        return self.__list.pop()
    # 头出队
    def pop_front(self) -> int:
        if self.empty():
            return -1
        return self.__list.pop(0)
    def front(self) -> int:
        if self.empty():
            return -1
        return self.__list[0]
    def size(self) -> int:
        return len(self.__list)
    def empty(self) -> bool:
        return self.size() == 0