I have been teaching (courses related to algorithms and complexity) for the past six years (five years as a PhD student at GeorgiaTech, and the past one year at Princeton). One of the most challenging and interesting part of teaching is creating new exercises to help teach the important concepts in an efficient way. We often need lots of problems to include in homeworks, midterms, final exams and also to create practice problem sets.
We do not get enough time to teach all the concepts in class because the number of hours/week is bounded. I personally like to teach only the main concepts in class and design good problem sets so that students can learn the generalizations or extensions of the concepts by solving problems hands-on. This helps them develop their own intuitions about the concepts.
Whenever I need a new exercise I hardly open a physical textbook. I usually search on internet and find exercises from a course website (or) “extract” an exercise from a research paper. There are hundreds of exercises “hidden” in pdf files across several course homepages. Instructors often spend lots of time designing them. If these exercises can reach all the instructors and students across the world in an efficiently-indexed form, that will help everybody. Instructors will be happy that the exercises they designed are not confined to just one course. Students will have an excellent supply of exercises to hone their problem-solving skills.
During 2008, half-way through my PhD, I started collected the exercises I like in a private blog. At the same time I registered the domain trueshelf.com to make these exercises public. In 2011, towards the end of my PhD, I started using the trueshelf.com domain and made a public blog so that anybody can post an exercise. [ Notice that I did not use the trueshelf.com domain for three years. During these three years I got several offers ranging upto $5000 to sell the domain. So I knew I got the right name 🙂 ] Soon, I realized that wordpress is somewhat “static” in nature and does not have enough “social” features I wanted. A screenshot of the old website is shown below.
The new version of TrueShelf is a social website enabling “crowd-sourcing” of exercises in any area. Here is the new logo, I am excited about 🙂
The goal of TrueShelf is to aid both the instructors and students by presenting quality exercises with tag-based indexing. Read the TrueShelf FAQ for more details. Note that we DO NOT allow users to post solutions. Each user may add his own “private” solution and notes to any exercise. I am planning to add more features soon.
In the long-run, I see TrueShelf becoming a “Youtube for exercises”. Users will be able to create their own playlists of exercises (a.k.a problem sets) and will be recommended relevant exercises. Test-preparation agencies will be able to create their own channels to create sample tests.
Feel free to explore TrueShelf, contribute new exercises and let me know if you have any feedback (or) new features you want to see. You can also follow TrueShelf on facebook, twitter and google+.
Let’s see how TrueShelf evolves.
My Brain is Open 
I think it’s an interesting idea. However, if it became at all “successful”, you can count on some students somewhere starting up a TrueShelfSolutions site, or some less obvious method of sharing solutions to the problems.
This is a problem of the Internet age that I’m unsure there’s a good solution for.
I hope in the long-run the advantages of Internet will eventually out-weigh its drawbacks.
Do you have a mechanism for citing the source of an exercise?
Hi Josephina, This is the next feature in my list. We will be adding a source field to each exercise.
Hi Josephina, This feature is now available on TrueShelf.
Great idea – I’ve wished for something like this for a while now, without being able to adequately pin down what it should look like. Glad to see this up, looks great and I am looking forward to adding this to the list of things that eat away countless evening hours before you know it!
Incidentally – while someone who is insistent on scouring the web for a solution is likely to be successful, it hasn’t stopped Project Euler and the like from being a source of excellent entertainment and learning for many hobbyists/students/teachers. The setup ensures that anyone who wants to have fun with it should be able to – accurate formulations for exercises, feedback, and at least not having the answers in-your-face 🙂
Thanks 🙂
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