标签：operation code pen family sem target ons round 思路
题目链接：https://leetcode.com/problems/implement-queue-using-stacks/
题目：Implement the following operations of a queue using stacks.
push
to top, peek/pop from top, size,
and is empty operations are valid./**
* 用两个栈模拟实现队列基本操作
* @author 徐剑
* @date 2016-02-25
*
*/
public class Solution
{
Stack<Integer> s1 = new Stack<>();
Stack<Integer> s2 = new Stack<>();
// Push element x to the back of queue.
public void push(int x)
{
s1.push(x);
}
// Removes the element from in front of queue.
public void pop()
{
if (!s2.empty())
{
s2.pop();
} else if (s1.isEmpty())
{
return;
} else
{
while (!s1.isEmpty())
{
int temp = s1.pop();
s2.push(temp);
}
s2.pop();
}
}
// Get the front element.
public int peek()
{
if (!s2.isEmpty())
return s2.pop();
else if (s1.isEmpty())
{
return -1;
} else
{
while (!s1.isEmpty())
{
int temp = s1.pop();
s2.push(temp);
}
return s2.peek();
}
}
// Return whether the queue is empty.
public boolean empty()
{
return s1.isEmpty() && s2.isEmpty();
}
}
【LeetCode OJ 232】Implement Queue using Stacks
标签：operation code pen family sem target ons round 思路
原文地址：http://www.cnblogs.com/gavanwanggw/p/7116016.html
