Question: Describe a variation of depth-first search that assigns the smallest available positive integer to a vertex when the algorithm is totally finished with this vertex. Show that in this numbering, each vertex has a larger number than its children and that the children have increasing numbers from left to right. Let T1 and T2 be spanning trees of a graph. The distance between T1 and T2 is the number of edges in T1 and T2 that are not common to T1 and T2.