leetcode 225. Implement Stack using Queues

解题思路：
用队列的基本操作实现栈的基本操作

原题目：

Implement the following operations of a stack using queues.

push(x) -- Push element x onto stack.
pop() -- Removes the element on top of the stack.
top() -- Get the top element.
empty() -- Return whether the stack is empty.
Notes:
You must use only standard operations of a queue -- which means only push to back, peek/pop from front, size, and is empty operations are valid.
Depending on your language, queue may not be supported natively. You may simulate a queue by using a list or deque (double-ended queue), as long as you use only standard operations of a queue.
You may assume that all operations are valid (for example, no pop or top operations will be called on an empty stack).

AC解，C++代码，菜鸟一个，请大家多多指正

class Stack {
public:
    queue<int> que;
    // Push element x onto stack.
    void push(int x) {
        que.push(x);
    }

    // Removes the element on top of the stack.
    void pop() {
        queue<int> tmp_que;
        while (que.size() != 1) {
            int value = que.front();
            que.pop();
            tmp_que.push(value);
        }
        que = tmp_que;
    }

    // Get the top element.
    int top() {
        return que.back();
    }

    // Return whether the stack is empty.
    bool empty() {
        return que.empty();
    }
};