During March 2025, contributed to the CodingTestStudy2/Daily_Morning_Coding_Test repository by developing a feature that calculates the maximum substring length where each character appears at most twice. This solution leveraged Java and applied algorithmic techniques such as the sliding window pattern, two pointers, and hashmap data structures to achieve O(n) time and O(K) space complexity. The implementation improved the platform’s ability to validate string constraints efficiently, resulting in faster and more scalable evaluation of candidate solutions. No major bugs were reported during this period, reflecting a focus on code quality, maintainability, and clear documentation throughout the development process.