Any website/textbook with problems+solutions in algorithms? I'm trying to find an online source or textbook with problems+solutions for problems in dynamic programming, number theory, graph theory, greedy algorithms, etc. Do you know of any?
Based on clarification in comments, Algorithms 4th ed. by Sedgewick and Wayne seems to meet your criteria. The book itself doesn't seem to have an official PDF version (I haven't searched for unofficial ones of dubious provenance), but the code is available both at the linked page and on Github, and includes solutions to selected exercises.