There are alot of solutions out there (mostly as pdf on Github or as answers on StackExchange). I do not try to list them all but only the most interesting ones (based on my personal opinion).
A word of warning: Take any solutions with a grain of salt (applies to my site too). Sometimes, after I solved a challenging exercise I try to google it to find out how others approach the problem. For each of these exercises the percentage of just wrong solutions was very high. Sometimes I couldn't find any correct solution. Even worse, some solutions gave the impression that the exercise is no big deal and the solution is straightforward (which might be true but at least their solution did not justify this).