[剑指offer]用两个栈实现队列

 1 class Solution
 2 {
 3 public:
 4     void push(int node) {
 5         while(!stack2.empty())
 6         {
 7           stack1.push(stack2.top());
 8           stack2.pop();
 9         }
10         stack1.push(node);
11     }
12 
13     int pop() {
14         while(!stack1.empty())
15         {
16           stack2.push(stack1.top());
17           stack1.pop();
18         }
19         int node = stack2.top();
20         stack2.pop();
21         return node;
22       }
23 private:
24     stack<int> stack1;
25     stack<int> stack2;
26 };