Maybe it's just me, but I find the problems on Open-CS poorly explained. For example, in problem 9, it asks to find a number in a matrix 'generated by the same

Maybe it's just me, but I find the problems on Open-CS poorly explained. For example, in problem 9, it asks to find a number in a matrix 'generated by the same algorithm', but neither does it tell what that algorithm is nor is it obvious how the algorithm works, given the examples. Similarly, in problem 20, some arbitrary tree is given with no explanation on how it is generated or what property it has, but you are asked to return the position of a given number in that tree. In problem 22, numbers are divided into substrings, which makes no sense. In Project Euler, the problems are carefully explained and demonstrated with a small example, so that you can concentrate on actually solving the problem instead of guessing what the author might have wanted.