int CountNum(Tree * T, int key)
// precondition: returns the number of nodes in Tree T    
//               with the value key.  Returns 0 if no
//               nodes contain key or if the tree is empty    
{
    int count = 0;
    if (T != NULL)
    {
	if (T->info == key)
	{
	    count++;
	}
	count += CountNum(T->left,key) + CountNum(T->right,key);
    }
    return count;
}