Developed and delivered depth-first search (DFS) based solutions for competitive programming problems in the hanaro-algorithm/algorithm repository, focusing on Operator Insertion for calculating maximum and minimum values and Safe Zones for identifying connected regions above water levels. Leveraged Java to implement modular DFS and backtracking templates, enhancing code reusability and clarity for similar algorithmic challenges. Addressed key edge cases and boundary conditions to ensure correctness and stability across diverse input scenarios. The work emphasized robust graph traversal utilities and clear interfaces, supporting rapid problem-solving and maintainability. All contributions were integrated with precise commit references, reflecting a methodical and reliable engineering approach.