Interview Question for Software Developer Engineer In Test at Microsoft:

int max(int a, int b)
{
  return (a >= b)? a: b;
}

int maxDepth(struct bTreeNode *root)
{
    if(root == NULL)
    {
        return 0;
    }
    else
    {
        int ld = maxDepth(root->lNode);
        int rd = maxDepth(root->rNode);
        if( ld > rd)
            return ld+1;
        else
            return rd+1;
    }
}

int diameter(struct bTreeNode *root)
{
    if(root == NULL)
    {
        return 0;
    }
    else
    {
        int ld = diameter(root->lNode);
        int rd = diameter(root->rNode);
        int lh = maxDepth(root->lNode);
        int rh = maxDepth(root->rNode);
        return max(lh + rh + 1, max(ld, rd));
    }
}