The problemset is persistent and some ranks are affected by number of solved problems. If the solutions are published it would be to easy to just copy the solution and submit it. Hence they will not be published. Authors are also requested not to publish their exact code. It is better and maybe more beneficial for everybody to discuss ideas and algorithms of solutions.
The code is visible to admins and the problem setter of the task he stated.
For some of the problems taken from competitions around the world it is probable that you may find a coded solutionon some other site. It is encouraged though that you understand the algorithm and code it yourself.
kfas