Recently I learn the dominator tree algorithm and I will like to solve some problem about this topic, if someone can help me with some link related to that, I be grateful. Thank in advance!!
UPD1: I found this problem disjoint water supply from 2013 ACM-ICPC Latin American Regional Contests maybe can be usefull, and thanks to marat.snowbear for this problems, very nice the second one.
http://www.codechef.com/MAY15/problems/GRAPHCNT
http://codeforces.net/gym/100513/problem/L