剑指Offer（二十）-- 包含min函数的栈

import java.util.Stack;

public class Solution {

    private Stack<Integer> datas = new Stack<>();
    private Stack<Integer> mins = new Stack<>();


    public void push(int node) {
        datas.push(node);
        if (mins.isEmpty()) {
            mins.push(node);
        } else {
            int min = mins.peek();
            if (node <= min) {
                mins.push(node);
            }
        }
    }

    public void pop() {
        if (datas.isEmpty()) {
            return;
        } else {
            int value = datas.peek();
            if (value == mins.peek()) {
                mins.pop();
            }
            datas.pop();
        }
    }

    public int top() {
        if(datas.isEmpty()){
            return -1;
        }
        return datas.peek();
    }

    public int min() {
        if(mins.isEmpty()){
            return -1;
        }
        return mins.peek();
    }
}