I will give all examples in ascending order, just change the judgement clause when you need descending order. $O(n^2)$ sorting algorithms Selection Sort The idea is, always select the smallest v...

LeetCode Problems 208. Implement Trie (Prefix Tree) 211. Design Add and Search Words Data Structure 212. Word Search II In previous problem, you should use DFS instead of BFS, or you will TLE. ...

Example 1 Never write: [[0] * 5] * 10 this clause you can only use once, [0] * 5, like this. But if you use [[0] * 5] * 10 instead of [[0]*5 for _ in range(10)], that will make your variable sh...

Very short conclusion: at least two traversal can uniquely a tree from the traversal, and one must be inorder traversal.

The problems come from the book A First Course in Probability by Sheldon Ross. But I am really sorry since I forgot where the solution I saw, maybe another book, Wikipedia, or maybe some other onli...

Personally, I believe the iPhone 17 is the most worthwhile option in the new series. Released on September 9, 2025, the iPhone 17 brings a significant balance between price and performance, much li...

At Seattle. Before landing, a warehouse? of Boeing. You know, Boeing is located at Seattle. Airbus A350-941 (reg N505DN) of Delta Airlines (DL). A very cutting-edge model, strongly recommend by ...

权限管理是开发中常见的场景，传统方法可能依赖数组、字典或数据库，尤其是在权限很多的情况下，大量的变量命名以及重复运用会增加代码的复杂度，而且更容易出错。今天分享如何用 位运算 来管理权限，包括 赋予、移除 和 检查 操作。 什么是位运算？ 位运算是直接对整数的二进制位进行操作的方式。Python 提供了多种位运算符，例如： &（按位与）：两个对应位都为 1 时结果为 1。 ...

因为我的博客是GitHub Pages搭建的，纯静态也主打迁移方便。当然今天写文章的时候报错了。 build The current runner (ubuntu-24.04-x64) was detected as self-hosted because the platform does not match a GitHub-hosted runner image (or tha...