Leetcode [Min Stack] java

Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.

• push(x) -- Push element x onto stack.
• pop() -- Removes the element on top of the stack.
• top() -- Get the top element.
• getMin() -- Retrieve the minimum element in the stack.

import java.util.Stack;class MinStack {    private Stack<Integer> stack = new Stack<Integer>();    private Stack<Integer> minStack = new Stack<Integer>();    public void push(int x) {        if(minStack.isEmpty() || minStack.peek()>=x) minStack.push(x);        stack.push(x);    }    public void pop() {        if(minStack.peek().equals(stack.peek())) minStack.pop();        stack.pop();    }    public int top() {        return stack.peek();    }    public int getMin() {        return minStack.peek();    }}

记录一下，非常简单的题目，第一次提交却失败了，原因是

minStack.peek().equals(stack.peek())

这里

一开始我用了==

但是其实这里没有自动拆箱，Integer比较要用equals，大意了