Diameter of a Binary Tree

Tree Diameter :The diameter of a tree (sometimes called the width) is the number of nodes on the longest path between two leaves in the tree.The diameter of G is defined as being the maximal distance in the graph.
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

/* Function to get diameter of a binary tree */

int diameter(struct node * tree)

{

   /* base case where tree is empty */

   if (tree == 0)

     return 0;

  /* get the height of left and right sub-trees */

  int lheight = height(tree->left);

  int rheight = height(tree->right);

  /* get the diameter of left and right sub-trees */

  int ldiameter = diameter(tree->left);

  int rdiameter = diameter(tree->right);

  /* Return max of following three

   1) Diameter of left subtree

   2) Diameter of right subtree

   3) Height of left subtree + height of right subtree + 1 */

  return max(lheight + rheight + 1, max(ldiameter, rdiameter));

}

Refer :  http://geeksforgeeks.org/?p=5687