Question: ind the two nodes in Binary Tree which have longest distance between them.

Should return I & C for following tree

A
/ \
B C
/ \
D E
/ \
F G
/
I


Solution: /*The second parameter is to store the height of tree.
Initially, we need to pass a pointer to a location with value
as 0. So, function should be used as follows:

int height = 0;
struct node *root = SomeFunctionToMakeTree();
int diameter = diameterOpt(root, &height); */
int diameterOpt(struct node *root, int* height)
{
/* lh --> Height of left subtree
rh --> Height of right subtree */
int lh = 0, rh = 0;

/* ldiameter --> diameter of left subtree
rdiameter --> Diameter of right subtree */
int ldiameter = 0, rdiameter = 0;

if(root == NULL)
{
*height = 0;
return 0; /* diameter is also 0 */
}

/* Get the heights of left and right subtrees in lh and rh
And store the returned values in ldiameter and ldiameter */
ldiameter = diameterOpt(root->left, &lh);
rdiameter = diameterOpt(root->right,&rh);

/* Height of current node is max of heights of left and
right subtrees plus 1*/
*height = max(lh, rh) + 1;

return max(lh + rh + 1, max(ldiameter, rdiameter));
}