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.empty())
10         {
11             while(!stack1.empty())
12             {
13                 stack2.push(stack1.top());
14                 stack1.pop();
15             }
16         }
17         if(!stack2.empty())
18         {
19             int tem = stack2.top();
20             stack2.pop();
21             return tem;
22         }
23         else
24         {
25             return -1;
26         }
27     }
28 
29 private:
30     stack<int> stack1;
31     stack<int> stack2;
32 };