包含min函数的栈

设置一个辅助栈，每当在栈中放入一个元素的时候，同时也在辅助栈中放入当前的最小值；
每当出栈的时候，同时将当前值和当前最小值出栈，代码如下：

import java.util.Stack;

public class Solution {

    Stack<Integer> stack = new Stack();
    Stack<Integer> minStack = new Stack();

    public void push(int node) {
        stack.push(node);
        if(minStack.isEmpty() || node < minStack.peek()){
            minStack.push(node);
        }else{
            minStack.push(minStack.peek());
        }
    }

    public void pop() {
        stack.pop();
        minStack.pop();
    }

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

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

参考：
https://blog.csdn.net/jsqfengbao/article/details/47260355
https://blog.csdn.net/u012289407/article/details/46564841