栈和队列(python)

栈:

1.First In Last Out(FILO)

2.先进后出,后进先出(桶/弹夹等)

python实现栈:

class Stack(object):
    def __init__(self):
        self.stack = []
    def pop(self):
        if self.is_empty():
            return None
        else:
            return self.stack.pop()
    def push(self,val):
        return self.stack.append(val)
    def peak(self):
        if self.is_empty():
            return None
        else:
            return self.stack[-1]
    def size(self):
        return len(self.stack)
    def is_empty(self):
        return self.size() == 0

s = Stack()
s.push(1)
s.peak()
s.is_empty()
s.pop()


队列:

1.First In First Out(FIFO)

2.先进先出

python实现:

class Queue(object):
    def __init__(self):
        self.queue = []
    def enqueue(self,val):
        self.queue.insert(0,val)
    def dequeue(self):
        if self.is_empty():
            return None
        else:
            return self.queue.pop()
    def size(self):
        return len(self.queue)
    def is_empty(self):
        return self.size() == 0

q = Queue()
q.enqueue(1)
q.is_empty()
q.dequeue()
需求:使用队列模拟栈/使用栈模拟队列

1.使用一个队列模拟栈:

class StackByQueue(object):
    def __init__(self):
        self.queue = Queue()
    def push(self, val):
        self.queue.enqueue(val)
    def pop(self):
        for i in range(self.queue.size() - 1):
            value = self.queue.dequeue()
            self.queue.enqueue(value)
        return self.queue.dequeue()


2.使用两个栈模拟队列:

class QueueByStack(object):
    def __init__(self):
        self.stack1 = Stack()
        self.stack2 = Stack()
    def enqueue(self, val):
        self.stack1.push(val)
    def dequeue(self):
        for i in range(self.stack1.size() - 1):
            value = self.stack1.pop()
            self.stack2.push(value)
        res = self.stack1.pop()
        for i in range(self.stack2.size()):
            value = self.stack2.pop()
            self.stack1.push(value)
        return res


 
posted @ 2020-03-16 18:36  以赛亚  阅读(122)  评论(0编辑  收藏  举报