Saved solutions for Leet Code, Code Forces, Hacker Rank, Project Euler, and Cracking The Coding Interview for studying. For Cracking The Coding Interview I initially did them on white board/paper and then copied them over. Generic data structure and specific algorithim implementations can be found in my Data-Structures-And-Algorithms repo: (https://github.com/MattiKemp/Data-Structures-And-Algorithms)
Mainly doing this because there has been several occasions where I wanted to go back to a problem I was working on but the website didn't save my solution or code properly. This is really important if I try implementing the problems in different ways: naive, optimized, best, recursive, or iterative soltuions. This also gives me good practice documenting, analyizing, and explaining my code and solutions.