225. 用队列实现栈
方法一
class MyStack(object):
def __init__(self):
"""
Initialize your data structure here.
"""
self.stack = []
def push(self, x):
"""
Push element x onto stack.
:type x: int
:rtype: void
"""
self.stack.append(x)
def pop(self):
"""
Removes the element on top of the stack and returns that element.
:rtype: int
"""
if len(self.stack) == 0:
return None
return self.stack.pop()
def top(self):
"""
Get the top element.
:rtype: int
"""
if len(self.stack) == 0:
return None
val = self.stack[-1]
return val
def empty(self):
"""
Returns whether the stack is empty.
:rtype: bool
"""
if len(self.stack) == 0:
return True
else:
return False
# Your MyStack object will be instantiated and called as such:
# obj = MyStack()
# obj.push(x)
# param_2 = obj.pop()
# param_3 = obj.top()
# param_4 = obj.empty()
