每日一练（剑指offer）包含min函数的栈

import java.util.Stack;

public class Solution {
    //用于栈的push 与 pop
    StackInteger> s1 = new StackInteger>();
    //用于存储最小min
    StackInteger> s2 = new StackInteger>();
    public void push(int node) {
        s1.push(node);
        //空或者新元素较小，则入栈
        if (s2.isEmpty() || s2.peek() > node)
            s2.push(node);
        else
            //重复加入栈顶
            s2.push(s2.peek());
    }

    public void pop() {
        s1.pop();
        s2.pop();
    }

    public int top() {
        return s1.peek();
    }

    public int min() {
        return s2.peek();
    }
}