Design and Analysis of Algorithms

A directed Hamiltonian cycle DHC in a directed graph G = (V, E) is a directed cycle of length n =|V|, where |V| is the number of vertices in G. So, the cycle goes through every vertex exactly once and then returns to the starting vertex. The DHC problem is to determine if a given directed graph G has a directed Hamiltonian cycle. Show that DHC is NP-Hard.