Where would I get tough C++ program for practice?

Question

I know basics of C++.I want to practice tough programs and increase my skills.

Answer 1

http://www.cplusplus.com/forum/articles/12974/
http://beginnerscpp.com/category/programming-challenges/
https://www.cprogramming.com/challenge.html

Answer 2

https://www.sololearn.com/Discuss/437973/?ref=app

Answer 3

If you want to practice more, try this project I did.
https://code.sololearn.com/WQNcLzN9R51S/?ref=app