包含min函数的栈（剑指offer-20）

 1 import java.util.Stack;
 2 
 3 public class Solution {
 4 
 5     private Stack<Integer> dataStack= new Stack<>();//数据栈
 6     private Stack<Integer> minStack= new Stack<>();//最小数的栈
 7 
 8     public void push(int node) {
 9         dataStack.push(node);
10         if(minStack.isEmpty() || minStack.peek()>dataStack.peek()){
11             minStack.push(dataStack.peek());
12         }
13         else minStack.push(minStack.peek());
14     }
15     
16     public void pop() {
17         if(!dataStack.isEmpty()) dataStack.pop();
18         if(!minStack.isEmpty()) minStack.pop();
19     }
20     
21     public int top() {
22         return dataStack.peek();// 取出数据栈的栈顶元素
23     }
24     
25     public int min() {
26         return minStack.peek();//取出含min函数的栈的栈顶元素
27     }
28 }