checking the order of binarytree

[qhdtls123]

I get stuck while I write codes about checking the order of binarytree.
here is what i got so far,

bool BinaryTree<int>::isOrdered(const BinaryTree& root)
{
bool order= false;

if(root->left != NULL)
{
isOrdered(root->left);
order = root > root-> left;
if(!order) return false;
}

else if(root->right !=NULL)
{
isOrdered(root->right);
order = root < root->right;
if(!order) return false;
}

else
return true;

return order;
}

There can be several errors but what I think the most problematic one is that it only compares the values of parent and child.

Actually I though about creating couple other helper functions to hold values.
but I wonder that there can be more efficient way.

Can you give me some ideas doing this? and also please let me know if there are other crucial errors

Thanks

[keskiverto]

"Ordered" as in BST? http://en.wikipedia.org/wiki/Binary_search_tree

Note: use of code tags makes commenting easier.

if (root->left != NULL) ...
else if (root->right !=NULL) ...

You do consider the right subtree only if the left subtree is empty.

bool BinaryTree<int>::isOrdered(const BinaryTree& root)
...
(root->left != NULL)
...
isOrdered(root->left);

Pointers are usually compared against value of NULL (whatever that is here), but const references are not.

Calling isOrdered(root->left); does nothing obvious, because its return value is not used.


Back to BST. There are three values of interest in a subtree of a potential BST:
* Is the subtree a valid BST?
* What are the smallest and largest keys of the subtree?

There are more than one way to traverse a tree.