c-ref

https://www.faceprep.in/c/c-programming-questions/

Simple https://www.w3resource.com/c-programming-exercises/array/index.php Array:

Secxond Largest DLeft Diagonal

Medium :

https://www.sanfoundry.com/c-program-tic-tac-toe-game/

Complex: https://www.geeksforgeeks.org/coin-change-dp-7/