Thread: AVL tree rotation

I'm trying to create AVL tree. So, a started with a binary tree and added a height value to it. Now, i'm trying to make the left and right rotations so it can balance itself. The binary tree and height value works fine, but i can't get the left rotate to work, and i'm a little confused about the psuedocode for it.
I was trying to follow this psuedocode from the book:

Code:

LEFT-ROTATE(T, x)
y<-right[x]
right[x]<-left[y]
if left[y] != nil[T]
   then p[left[y]]<-x
p[y]<-p[x]
if p[x] = nil[T]
   then root[T]<-y
   else if  x = left[p[x]]
              then left[p[x]] = y
              else right[p[x]] = y
left[y]<-x
p[x]<-y

where T is the tree and x is the node the rotation is done on.
For the nil[T], is this just suppose to be NULL?
And, i'm not sure what is suppose to go here:

Code:

then root[T]<-y

So, i'm a little unclear about the T in this code. It has T as a parameter, but i don't understand how you pass in the whole tree.
Here is what i have (it doesn't work correctly)

Code:

int LeftRotate(candidate *root, candidate *x)
{
	candidate *y;
	y = x->right;
	x->right = y->left;

	if(y->left != NULL)
	{
		y->left->parent = x;
	}

	y->parent = x->parent;

	if(x->parent == NULL)
	{
		root = y;
	}
	else if(x = x->parent->left)
	{
		x->parent->left = y;
	}
	else
	{
		x->parent->right = y;
	}

	y->left = x;
	x->parent = y;

	return 0;
}

Here is my main:

Code:

int main(int argc, char* argv[])
{
	ifstream inFile ( argv[1] );

	if ( !inFile.is_open() )
	{
		cout << "Could not open file." << endl;
	}
	else
	{
		char name[20];
		int count = 0;

		candidate *root;
		root = NULL;


		
		while(!inFile.eof())
		{
			//Flag determines if name has been found in search.
			int flag = 0;
							
			inFile.getline(name, 20);
			//Change all upper-case letter to lower-case, so they will count as the same name.
			LowerCase(name, count);

			//If name is already in tree, increase votes.
			TreeSearch(root, name, flag);
			
			//If name is not already in tree, insert it.
			if(flag == 0)
			{
				TreeInsert(root, name, flag);
			}			
		}

		//Make copy of original root
		candidate *root2;
		root2 = root;		
				
		LeftRotate(root2, root);		
		cout << endl;


		cout << endl;
		//Print tree in-order (alphabetical).
		PrintTree(root);		
	}	

	cin.get();
	return 0;
}

Everything in and above the while loop is fine.
I thought maybe i was suppose to send in the root of the tree along with the node being rotated, so i duplicated the root node, and passed it in, but i guess that's not correct. So, all the code that is red, i'm not sure what i should be putting there. Any suggestions on how to fix this function?

Thanks

PS: If it looks familiar, it's the same as my hash program, except i'm using an AVL tree instead of a hash table.