@Override
        public int hashCode() {
            int result = currentVertex;
            result = 31 * result + (vertexSet != null ? vertexSet.hashCode() : 0);
            return result;
        }
Date 11/17/2015
@author Tushar Roy

Help Karp method of finding tour of traveling salesman.

Time complexity - O(2^n * n^2)
Space complexity - O(2^n)

https://en.wikipedia.org/wiki/Held%E2%80%93Karp_algorithm
src/com/interview/graph/TravelingSalesmanHeldKarp.java