The algorithms presented above all rely on O(1) time access to the size of the shared leaf set |F ∩ G| for any pair of subtrees F of T and G of T', where F and G each has size at least two, i.e. contains more than a single leaf. We will refer to |F ∩ G| as the intersection size of subtree F and G. In [9] and O(n2) time and space algorithm is presented for computing the intersection sizes of all pairs of subtrees F and G of two binary input trees. A straightforward generalization of this algorithm to two input trees T and T' of arbitrary degrees results in an O(n2dd') time and O(n2) space algorithm, which gives a worst case running time of O(n4).