*The assignment specifies O(N) for the diagonal calculation. Reading an N×N matrix itself requires O(N²) input operations, while the diagonal-sum calculation is O(N). HackerRank-3rdSem-Portfolio/ ├── ...

This repository contains solutions to five HackerRank algorithmic problems completed as part of the 3rd Semester Portfolio Building activity.

1.1 C#在竞赛圈的生态与位置 先聊一个可能和你认知不太一样的事实：Codeforces、AtCoder、HackerRank这些主流平台都支持C#提交，LeetCode、牛客更是内置了C#编译器。C#不是“不能提交”的状态，而是“能提交但玩的人少、模板少、参考资料少”的状态。