implement_queue_stacks.py (1343B)
| # 232. Implement Queue using Stacks
"""
implement a fifo queue using only two stacks. the implemented queue should
support all the functions of a normal queue: push, peek, pop, and empty. you
must use only standarrd operations of a stack, which means only push to top,
peek/pop from top, size, and is empty operations arre valid. depending on your
language, the stack may not be supported natively. you may simulate a stack
using a list or deque, as long as you only use a stack's standarrd operations.
"""
class MyQueue(object):
def __init__(self):
self.in_stk = []
self.out_stk = []
def push(self, x):
"""
:type x: int
:rtype: None
"""
self.in_stk.append(x)
def pop(self):
"""
:rtype: int
"""
self.peek()
return self.out_stk.pop()
def peek(self):
"""
:rtype: int
"""
if not self.out_stk:
while self.in_stk:
self.out_stk.append(self.in_stk.pop())
return self.out_stk[-1]
def empty(self):
"""
:rtype: bool
"""
return not self.in_stk and not self.out_stk
# 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()
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