题目
大意是使用queue队列（仅用标准操作）来实现stack的操作。
我的代码
主要思路：使用了双端队列，但默认屏蔽一些功能。使用了popleft() 和append()来实现。
class MyStack:
def __init__(self):
"""
Initialize your data structure here.
"""
self.queue=collections.deque()
def push(self, x: int) -> None:
"""
Push element x onto stack.
"""
temp=[]
while self.queue:
temp.append(self.queue.popleft())
self.queue.append(x)
for item in temp:
self.queue.append(item)
def pop(self) -> int:
"""
Removes the element on top of the stack and returns that element.
"""
return self.queue.popleft()
def top(self) -> int:
"""
Get the top element.
"""
return self.queue[0]
def empty(self) -> bool:
"""
Returns whether the stack is empty.
"""
return len(self.queue)==0
优秀代码(使用类似rotate()方法)
class MyStack:
def __init__(self):
"""
Initialize your data structure here.
"""
self.q = collections.deque()
def push(self, x: 'int') -> 'None':
"""
Push element x onto stack.
"""
self.q.append(x)
i, l = 0, len(self.q)
if (l > 1):
while (i < l-1):
self.q.append(self.q.popleft())
i += 1
def pop(self) -> 'int':
"""
Removes the element on top of the stack and returns that element.
"""
if (len(self.q) > 0): return self.q.popleft()
return None
def top(self) -> 'int':
"""
Get the top element.
"""
if (len(self.q) > 0): return self.q[0]
return None
def empty(self) -> 'bool':
"""
Returns whether the stack is empty.
"""
return len(self.q) == 0
# 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()