摘要： 原题链接在这里：https://leetcode.com/problems/binary-tree-preorder-traversal/ 题目： Given a binary tree, return the preorder traversal of its nodes' values. For 阅读全文

摘要： 原题链接在这里: https://leetcode.com/problems/min-stack/ 题目： Design a stack that supports push, pop, top, and retrieving the minimum element in constant time 阅读全文