h2. Additional problems

# *Friend of a friend*(interview question) Given two user names in a social network design an efficient way to test if one is a friend of a friend of the other.

# *Friend of a friend*(interview question) Given two user names in a social network find design an efficient way to test if one is a friend of a friend of the other.

# *Equal partition* Given a set A of 40 real numbers, find out if there is any way to split A in two sets such that the sums of their elements are equal. (Hint: complexity $O(2^n/2^)$)
# *Minimal vertex cover* Given a graph of n nodes (n <= 30), find out a set with the smallest number of vertices such that each edge in the  graph has at least one node inside the set. (Hint: complexity $O(3^n/2^)$)
# *Square fence* You're given an array L which represents the lengths of n planks. You have to answer if there's any way to form the edges of a square fence using all the planks without breaking or overlapping them.  (Hint: complexity $O(4^n/2^)$)