Faster algorithms for finding lowest common ancestors in directed acyclic graphs
We present two new methods for finding a lowest common ancestor (LCA) for each pair of vertices of a directed acyclic graph (dag) on n vertices and m edges. The first method is surprisingly natural and solves the all-pairs LCA problem for the input dag on n vertices and m edges in time 0 (n m). The second method relies on a novel reduction of the all-pairs LCA problem to the problem of finding max