Question

Is there a built-in method in boost to find the lowest common ancestor of two or more nodes in a tree (which is a boost::graph instance)?

If not, I would appreciate suggestions on the best way to do this. Wikipedia claims there are efficient algorithm to achieve this in O(1) time (with O(n) pre-processing), but it doesn’t describe the algorithms.

Answer 1

Found the algorithm in Wikipedia:

 function TarjanOLCA(u)
 MakeSet(u);
 u.ancestor := u;
 for each v in u.children do
     TarjanOLCA(v);
     Union(u,v);
     Find(u).ancestor := u;
 u.colour := black;
 for each v such that {u,v} in P do
     if v.colour == black
         print "Tarjan's Least Common Ancestor of " + u +
               " and " + v + " is " + Find(v).ancestor + ".";