A greedy approximation algorithm for the longest path problem in   undirected graphs
  In graph theory, the longest path problem is the problem of finding a simple path of maximum length in a given graph. For some small classes of graphs, the problem can be solved in polynomial time [2, 4], but it remains NP-hard on general graphs, since it includes the Hamiltonian path problem as a special case [3]. Motivated by finding a simple, quick algorithm for finding long paths in large graphs, in this paper we show a greedy algorithm with a time complexity of O(n^2 (n+m)), where n is the number of the vertices and m is the number of edges. 
Lajos L. Pongr\'acz
cs.DS