Dimethyl Blog

This is a note for CS2501 Discrete Mathematics (离散数学) for information security major in SJTU. It is originally written in Chinese to keep consistency with the course language, and later translated to English.

Discrete mathematics mainly contains 3 parts: graph theory, logic, and set theory. Graph theory introduces basic concept of graphs, eulerian and hamiltonian paths and circuits, trees and spanning trees. Logic part introduces propositional logic and predicate logic, including syntax, semantics, equivalence, and inference. Set theory part introduces basic set concepts, relations, functions, and combinatorics.

Introduction

Installing Arch Linux is not an esay thing in any way, especially for a dual-booting system. Ensure you grasp basic skills of searching and asking questions, and basic English reading profession to read warning and error messages.

Also, this post records some issues encountered in usage of dual-booting Arch Linux and Windows systems, and their solutions. Check them in the last section Possible Issues During Normal Usage.

Steps and delicacies in 2025. See more in Masonry Collection.

Another year in postcrossing and here is the digest of 2025. Check my postcard activities at Collections/Postcards.

Slow Mail in a Fast World: 2025 Overview

The transition from high school to university is often described as a leap, but for me, it felt more like a shift in time zones. Suddenly, the rhythm of life accelerated. Looking back at the Spring semester of 2024 and the Fall semester of 2025, the blur of academic rigors, orientation events, and the sheer mental load of “First Year” adjustments took center stage.

Here is a digest of the postcrossing postcards I’ve sent in 2024. My postcard activities can be found on Collections/Postcards.

This post introduces how to display a postcard map in a Hexo blog using data exported from Postcrossing or in a custom format.

This is a write-up for ZJUCTF 2025. The original challenge descriptions can be found at https://mp.weixin.qq.com/s/Z91DTlJtvWClyCfnHpXTOQ for ZJU students or https://notes.sjtu.edu.cn/s/nji8es_7e for SJTU students.

All solution code and some challenge files referenced below are collected in the repository MingchenDai/ZJUCTF-2025.

Some notes on C++ STL.

This post is aimed to record some interesting LeetCode problems.

Reference: Regular Expressions Tutorial

Regular expressions is a sequence of characters that forms a search pattern and own common shortands regex or regexp.

Engines are programs that can process regular expressions, trying to match the pattern to the given string. Different engines may have different syntax and features.