If you want to see the problems under the tag dp you usually type: http://mirror.codeforces.com/problemset/tags/dp
I found out just now that to see the problems under the tag (dp + trees) or (dp + games) you should type:
http://mirror.codeforces.com/problemset/tags/dp,trees or http://mirror.codeforces.com/problemset/tags/dp,games