232.用栈实现队列

注意：

1，构造函数不需要

2，需要有两个成员变量 in out

代码：

 1 class MyQueue {
 2 public:
 3 stack<int> in;
 4     stack<int>out;
 5     MyQueue() {
 6 
 7     }
 8     
 9     void push(int x) {
10 in.push(x);
11     }
12     
13     int pop() {
14 if (out.empty())
15     {
16         while (in.empty() != true)
17         {
18             out.push(in.top());
19             in.pop();
20         }
21     }
22     
23     int result = out.top();
24     out.pop();
25     return result;
26     }
27     
28     int peek() {
29     int result = pop();
30     out.push(result);
31 
32     return result;
33     }
34     
35     bool empty() {
36 if (out.empty() && in.empty())
37         return true;
38     
39     return false;
40     }
41 };
42 
43 /**
44  * Your MyQueue object will be instantiated and called as such:
45  * MyQueue* obj = new MyQueue();
46  * obj->push(x);
47  * int param_2 = obj->pop();
48  * int param_3 = obj->peek();
49  * bool param_4 = obj->empty();
50  */