[5] to prove safety offer. Two stacks to queue [by Python]

GitHub：https://github.com/cytues/sword

Source

Title Description

Two stacks to achieve a queue, the completion queue Push and Pop operations. Queue elements int.

  
  
# -*- coding:utf-8 -*-
'' '
A is a push, B is out of the stack, when the stack, can go directly to A, while the stack, to determine whether there is an element,
If no element B, pop is certainly an error, it should first of all A elements inside overwhelm B, an element and then pop the top, if B has direct pop out, you can,
This is the best idea, two stacks achieved last out, together and achieve a FIFO queue.
' ''
class Solution:
# Initialize two stacks
def __init__(self):
self.stackA = []
self.stackB = []
# Achieved here only requires the push and pop operations queues are used respectively, and two press-pop stack represents
def push(self, node):
# write code here
self.stackA.append(node)
# Pop requires a priori conditions: If the queue is empty, None is returned
def pop(self):
# If there is an element of the stack is pushed directly pop
if self. stackB:
self.stackB.pop()
A # If there are no elements Returns None
elif Note self . stack:
return None
# If all elements A, B into the uniform press-pop performed
else:
while self. stackA:
self.stackB.append( self.stackA.pop())
return self.stackB.pop()
  
  

 

GitHub：https://github.com/cytues/sword