int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified (thus it tries to convert a const this to a non-const this) (int getTreeHeight() const also has this problem, and other functions may too, which I don't have time to validate). If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&, or rather it should probably take a const DListNode<T>*).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.

And there's no reason int height(DListNode<T>* &p) should take a reference to a pointer. Just taking a pointer would suffice.

int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified (int getTreeHeight() const also has this problem, and other functions may too, which I don't have time to validate). If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&, or rather it should probably take a const DListNode<T>*).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.

And there's no reason int height(DListNode<T>* &p) should take a reference to a pointer. Just taking a pointer would suffice.

int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified (int getTreeHeight() const also has this problem, and other functions may too, which I don't have time to validate). If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.

And there's no reason int height(DListNode<T>* &p) should take a reference to a pointer. Just taking a pointer would suffice.

int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified. If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.

int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified. If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.

int getTreeNodeCount() const is marked as const (i.e. it guarantees it won't modify the object). It attempts to call int nodeCount(DListNode<T>& node), which is not marked as const, and therefore cannot guarantee the object isn't modified. If getTreeNodeCount() is to remain const, nodeCount(DListNode<T>& node) needs to be marked as const (and should probably take a const DListNode<T>&).

Also, note that nodeCount() takes a DListNode<T>&, but rootNode is a DListNode<T>*. They're not the same thing.

But that error doesn't match the file you posted. It says the error is on line 66 and is with BinaryTree<T>::height, but line 66 is int getTreeNodeCount() const.