A collection of C challenges I've written categorized by difficulty. If you have any questions, contact me on Discord (CntKillMe#2648). If there's an issue in any of the challenges (i.e. typo, misinformation, ambiguity, etc.), feel free to file an issue.
It is expected you are sufficiently fluent in C. If you want, you may implement these projects in C++ and make use of their language features but you will have to adjust the test cases to fit your implementation. All C99 standard library functions are fair game unless explicitly stated. No outside libraries or compiler extensions/intrinsics are allowed unless explicitly stated. If you're solving the challenges in C++, refrain from using the C++ standard library if they essentially solve the problem for you.