The diameter of a tree T is the largest of the following quantities:

* the diameter of T's left subtree
* the diameter of T's right subtree
* the longest path between leaves that goes 
  through the root of T (this can be computed 
  from the heights of the subtrees of T) 

In C, with suitable Node and Tree structs, you could implement it as:

int diameter(Tree * t) // post: return diameter of t { if (t == 0) return 0; int lheight = height(tree->left); int rheight = height(tree->right); int ldiameter = diameter(tree->left); int rdiameter = diameter(tree->right); return max(lheight + rheight + 1, max(ldiameter,rdiameter)); }

Implement the Diameter computation in a structure-shy way
using DemeterF. Do one traversal of the tree to compute
both height and diameter.

Your function object must correctly compute the diameter for both
cd-pure and cd-with noise from question ?.

Find the UNKNOWN below:

From the class dictionary:

DiameterPair = "height" <height> int "diameter" <diameter> int.


From the function object:

class Diameter extends IDba{ // type unifying 
    DiameterPair combine(BSTInt l) {return new DiameterPair(0,0);}
    UNKNOWN
    DiameterPair combine(NodeInt t, Integer d, DiameterPair l, DiameterPair r){ return 
      new DiameterPair(Math.max(l.get_height(), r.get_height())+1, 
        Math.max(l.get_height() + r.get_height() +1, Math.max(l.get_diameter(), r.get_diameter()))); 
    }
}