Why this function dosn't work?

Question

This function gets a binary tree and returns the height of it, when the program runs it results in an error because the function recursion gets a null tree, how do i fix it, and is there a better way to find the height of the tree? I know i should check each sub tree in each size but i couldn't figure a way to do it.

template <class T> int GetHeightOfTree(BinTreeNode<T> top)
{
if (&top == NULL)
return -1;
return 1 + fmax(GetHeightOfTree(*top.GetLeft()), GetHeightOfTree(*top.GetRight()));
}

Answer 1

Bennett Post Ill try it ,thanks