Research on space efficient graph algorithms, particularly for st-connectivity, has a long history including the celebrated polynomial time, O(lg n) bits 3 algorithm in undirected graphs by Reingold (JACM 2008), and polynomial time, n/2 Θ( Some of these results were announced in preliminary form in the proceedings of 22nd International Computing and Combinatorics Conference (COCOON 2016), Springer LNCS volume 9797, pages 119-130 [7], and 27th International Symposium on Algorithms and Computation (ISAAC 2016), LIPIcs, volume 64, pages 22:1-22:13 [17]. More specifically, this paper contains the linear time algorithms for DFS and its applications, announced in [7] and [17], along with the linear time algorithms for BFS and a few other graph problems, announced in [7]. 3 We use lg to denote logarithm to the base 2.