232. 用栈实现队列
方法一
class MyQueue(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.stack1 = []
self.stack2 = []
def push(self, x):
"""
Push element x to the back of queue.
:type x: int
:rtype: void
"""
self.stack1.append(x)
def pop(self):
"""
Removes the element from in front of queue and returns that element.
:rtype: int
"""
if self.stack2:
return self.stack2.pop()
else:
while self.stack1:
e = self.stack1.pop()
self.stack2.append(e)
return self.stack2.pop()
def peek(self):
"""
Get the front element.
:rtype: int
"""
if self.stack2:
return self.stack2[len(self.stack2) - 1]
else:
while self.stack1:
e = self.stack1.pop()
self.stack2.append(e)
return self.stack2[len(self.stack2) - 1]
def empty(self):
"""
Returns whether the queue is empty.
:rtype: bool
"""
if len(self.stack1) == 0 and len(self.stack2) == 0:
return True
else:
return False
# Your MyQueue object will be instantiated and called as such:
# obj = MyQueue()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.peek()
# param_4 = obj.empty()
"""
- push(x) -- 将一个元素放入队列的尾部。
- pop() -- 从队列首部移除元素。
- peek() -- 返回队列首部的元素。
- empty() -- 返回队列是否为空。
"""
