题解 | 包含min函数的栈

import java.util.*;
import java.util.Stack;

public class Solution {
    Stack<Integer> numbers = new Stack<>();

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

    
    public void push(int node) {
        if (numbers.isEmpty()) {
            numbers.push(node);
            minStack.push(node);
        } else {
            numbers.push(node);
            if (node < minStack.peek()) {
                minStack.push(node);
            } else {
                minStack.push(minStack.peek());
            }
        }
    }
    
    public void pop() {
        numbers.pop();
        minStack.pop();
    }
    
    public int top() {
        return numbers.peek();
    }
    
    public int min() {
        return minStack.peek();
    }
}