You can find around 400+ data structure and algorithms problems here http://www.techiedelight.com/list-of-problems/ in C/C++ that are helpful to improve your algorithmic skills and also to crack coding interview of top tech companies.
Below's another link that filters problems that are solved using STL.
http://www.techiedelight.com/data-structures-and-algorithms-interview-questions-stl/
Hope this helps.