辅助栈存储最小元素,与力扣(剑指 Offer 30. 包含min函数的栈)相同

import java.util.*;

public class Solution {

    private Stack<Integer> A = new Stack<>();
    private Stack<Integer> B = new Stack<>();

    public void push(int node) {
        A.push(node);
        if (B.isEmpty() || B.peek() >= node) B.push(node);
    }

    public void pop() {
        if (B.peek().equals(A.pop())) B.pop();
    }

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

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