This repository is a personal collection of study notes and PDF papers focused on large language models for recommendation systems (LLM4Rec). It contains markdown notes summarizing topics such as SNS-based LLM post-training, vocabulary customization for LLMs, LLM-to-SQL techniques, and algorithm explanations (e.g., longest palindrome substring). The majority of files are PDF research papers and reference materials, with no source code, configuration, or executable components. The content serves as a reference library for the maintainer's learning and interview preparation.