4. (10 points) For this problem, a full binary tree is a rooted tree where every node x is either a leaf or it has exactly two children le f t(x) and right(x). Full binary tree T has a complete top of depth d if for each i E {0, . . .,d}, row i has the maximum possible 21 nodes. Figure 1. A full binary tree with a complete top of depth 3. Describe and analyze an algorithm that given a full binary tree T with root node r, computes the largest value d for which T has a complete top of depth d. You do not need to justify correctness of your algorithm. Advice: Recursively solve the problem on le f 1'0") and right(r)'s subtrees