During June 2025, Seungwoo Jung developed foundational algorithm and data structure content for the krafton-jungle/KJ-ALGO-BOOK-9-303 and KJ-DS-BOOK-9-303 repositories. He implemented Python-based examples for Bellman-Ford and Topological Sort, providing clear explanations and problem descriptions to support learning. In the data structures repository, he introduced a Segment Tree with detailed documentation, covering both direct value replacement and difference-based update strategies. Seungwoo also maintained repository quality by reverting draft content when necessary. His work demonstrated strong skills in Python, algorithm implementation, and documentation, establishing a robust base for future chapters and improving onboarding for the KJ-BOOK series.