During October 2024, Donghwan Lee developed two Java-based solutions in the onestone11/kosa-study-tigger repository, focusing on practical classroom and operational challenges. He implemented a coin change calculator for Japanese yen using a greedy algorithm, efficiently minimizing coin usage for a fixed amount. Additionally, he created a gym clothes distribution program that maximizes student participation by handling array manipulation and edge-case borrowing scenarios. Both features emphasized maintainability, clear input/output handling, and quick testability. Donghwan demonstrated proficiency in Java, algorithm design, and problem decomposition, delivering standalone, reusable code that supports both immediate classroom needs and potential future coursework applications.