【剑指OFFER】用两个栈实现队列

 1 import java.util.Stack;
 2 
 3 public class Solution {
 4     Stack<Integer> stack1 = new Stack<Integer>();
 5     Stack<Integer> stack2 = new Stack<Integer>();
 6     
 7     public void push(int node) {
 8         stack1.push(node);
 9     }
10     
11     public int pop() {
12         if (stack2.isEmpty()) {
13             while (!stack1.isEmpty()) {
14                 stack2.push(stack1.pop());
15             }
16         }
17         return stack2.pop();
18     }
19 }