AVLNode removeNode(AVLNode root, String wordToRemove)
{
// STEP 1: PERFORM STANDARD BST DELETE
if (root == null)
{
return(root);
}
// If the key to be deleted is smaller than
// the root's key, then it lies in left subtree
if (strcmp(wordToRemove, root.word.word) < 0)
{
root.leftNode = removeNode(root.leftNode, wordToRemove);
}
// If the key to be deleted is greater than the
// root's key, then it lies in right subtree
else if (strcmp(wordToRemove, root.word.word) > 0)
{
root.rightNode = removeNode(root.rightNode, wordToRemove);
}
// if key is same as root's key, then this is the node
// to be deleted
else
{
// node with only one child or no child
if ((root.leftNode == null) || (root.rightNode == null))
{
AVLNode temp = null;
if (temp == root.leftNode)
{
temp = root.rightNode;
}
else
{
temp = root.leftNode;
}
// No child case
if (temp == null)
{
temp = root;
root = null;
}
else // One child case
{
root = temp; // Copy the contents of
}
// the non-empty child
}
else
{
// node with two children: Get the inorder
// successor (smallest in the right subtree)
AVLNode temp = minValueNode(root.rightNode);
// Copy the inorder successor's data to this node
root.word = temp.word;
// Delete the inorder successor
root.rightNode = removeNode(root.rightNode, temp.word.word);
}
}
// If the tree had only one node then return
if (root == null)
{
return(root);
}
// STEP 2: UPDATE HEIGHT OF THE CURRENT NODE
root.height = max(height(root.leftNode),
height(root.rightNode)) + 1;
// STEP 3: GET THE BALANCE FACTOR
// OF THIS NODE (to check whether
// this node became unbalanced)
int balance = getBalance(root);
// If this node becomes unbalanced,
// then there are 4 cases
// Left Left Case
if (balance > 1 && getBalance(root.leftNode) >= 0)
{
return(rightRotate(root));
}
// Left Right Case
if (balance > 1 && getBalance(root.leftNode) < 0)
{
root.leftNode = leftRotate(root.leftNode);
return(rightRotate(root));
}
// Right Right Case
if (balance < -1 && getBalance(root.rightNode) <= 0)
{
return(leftRotate(root));
}
// Right Left Case
if (balance < -1 && getBalance(root.rightNode) > 0)
{
root.rightNode = rightRotate(root.rightNode);
return(leftRotate(root));
}
return(root);
}
public void insert(String word, Location location)
{
this.root = insertUtility(this.root, word, location);
}
AVLNode insertUtility(AVLNode node, String wordToAdd, Location location)
{
/* 1. Perform the normal BST insertion */
if (node == null)
{
Word word = new Word(wordToAdd, location);
return(new AVLNode(word));
}
// MessageBox.Show(wordToAdd + " " + node.word.word);
if (strcmp(wordToAdd, node.word.word) < 0)
{
node.leftNode = insertUtility(node.leftNode, wordToAdd, location);
}
else if (strcmp(wordToAdd, node.word.word) > 0)
{
node.rightNode = insertUtility(node.rightNode, wordToAdd, location);
}
else
{
node.word.count++;
node.word.locations.AddLast(location);
}
/* 2. Update height of this ancestor node */
node.height = 1 + max(height(node.leftNode),
height(node.rightNode));
/* 3. Get the balance factor of this ancestor
* node to check whether this node became
* unbalanced */
int balance = getBalance(node);
// If this node becomes unbalanced, then there
// are 4 cases Left Left Case
if (balance > 1 && strcmp(wordToAdd, node.leftNode.word.word) < 0)
{
return(rightRotate(node));
}
// Right Right Case
if (balance < -1 && strcmp(wordToAdd, node.rightNode.word.word) > 0)
{
return(leftRotate(node));
}
// Left Right Case
if (balance > 1 && strcmp(wordToAdd, node.leftNode.word.word) > 0)
{
node.leftNode = leftRotate(node.leftNode);
return(rightRotate(node));
}
// Right Left Case
if (balance < -1 && strcmp(wordToAdd, node.rightNode.word.word) < 0)
{
node.rightNode = rightRotate(node.rightNode);
return(leftRotate(node));
}
/* return the (unchanged) node pointer */
return(node);
}
