Hi everybody I am beginner developer and I was wondering if you store the algorithms lets say on paper or in the computer once you are done solving a problem or do you just wait if a similar problem and jump into solving it again? Thanks!

if you store the algorithms

Since all my projects are in source control, yes, I store them. The hard part is remembering in which project you solved something.

solving it again

Don't repeat yourself.

From a more computer science prospective, yes and no. Most of the problems I encounter are problems that can be solved by adapting an already explored algorithm (or sometimes it's more of a mathematical therum). I do keep all my Math and Computer Science textbooks, along with a digital collection of my notes and other material. If I need to create a more ad-hoc algorthm, generally it's not usefull outside of the application, so I won't create a space for it in my "library". If I created an algorithm that might be usefull outside of a specific application, I'd probably write more formal paper on it, and potentially publish it if it's usefull.

Like pritaeas, I store all of my personal projects into one revision control.