JZ20 包含 min 函数的栈

https://www.nowcoder.com/practice/4c776177d2c04c2494f2555c9fcc1e49

这题关键就是添加一个最小栈同步插入弹出数据

import java.util.Stack;

public class Solution {
    private Stack<Integer> dataStack = new Stack<>();
    private Stack<Integer> minStack = new Stack<>();
    
    public void push(int node) {
        dataStack.push(node);
        
        if (minStack.empty() || minStack.peek() > node) {
            minStack.push(node);
        } else {
            // 这里是使辅助栈和数据栈个数保持一致
            minStack.push(minStack.peek());
        }
    }
    
    public void pop() {
        dataStack.pop();
        minStack.pop();
    }
    
    public int top() {
        return dataStack.peek();
    }
    
    public int min() {
        return minStack.peek();
    }
}