Getting good at LeetCode Java can feel like a puzzle sometimes, right? You see all these problems, and you’re not sure where to even start. This guide is here to break down the common approaches and ...

If you’ve ever searched for ways to practice coding or prep for tech interviews, you’ve probably seen LeetCode mentioned everywhere. But in 2025, is LeetCode free, or do you have to pay to get ...

* Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).

你在面试中会遇到的那种算法题，AI已经能自己解决了，比如下面这道题： 对于一个记录论文引用次数的数组，每个元素都是非负整数。请写出函数h_index，输出这些论文的h指数，即至多有h篇文章被至少引用了h次。 除了排序没用counts.sort(reverse = True)让人看着 ...

This book is notes about learning data structure and algorithm. It was written in Simplified Chinese but other languages such as English and Traditional Chinese are also working in progress.