用两个栈实现队列

 1 class Solution
 2 {
 3 public:
 4     void push(int node) {
 5         stack1.push(node);
 6     }
 7 
 8     int pop() {
 9         if(stack2.size()<=0){
10             while(stack1.size()){
11                 int data = stack1.top();
12                 stack1.pop();
13                 stack2.push(data);
14             }
15         }
16         int head = stack2.top();
17         stack2.pop();
18         return head;
19     }
20 
21 private:
22     stack<int> stack1;
23     stack<int> stack2;
24 };