public void insert(AVLNode node)
{
//Go down BST and insert the node
node.Height = 0;
node.Balance = 0;
if (root == null)
{
root = node;
return;
}
else
{
AVLNode curNode = root;
bool nodeInserted = false;
//Loop until inserted setting curNode to the inserted node
while (nodeInserted == false)
{
if (node.Key <= curNode.Key)
{
if (curNode.LeftChild == null)
{
curNode.setLeftChild(node);
nodeInserted = true;
}
curNode = curNode.LeftChild;
}
else
{
if (curNode.RightChild == null)
{
curNode.setRightChild(node);
nodeInserted = true;
}
curNode = curNode.RightChild;
}
}
//Recursively go back up the tree and check and set the balances and heights of nodes
setAndCheckBalanceAndHeights(curNode);
}
}
public void setAndCheckBalanceAndHeights(AVLNode curNode)
{
int insertedKey = curNode.Key;
//Cycle through all the nodes until the root is reached
while (curNode.Parent != null)
{
AVLNode parent = curNode.Parent;
curNode = curNode.Parent;
//Set balance and height of current node's parent
setBalanceAndHeight(parent);
//Check for imbalance
if (Math.Abs(parent.Balance) > 1)
{
Console.Write("Imbalance occured at inserting ISBN " + insertedKey + ";");
//Check if left imbalance, else right imbalance
if (parent.Balance > 1)
{
AVLNode leftChild = parent.LeftChild;
//Check if left subtree heavy, else right subtree heavy
if (leftChild.Balance > 0)
{
Console.WriteLine("fixed in right rotation");
AVLNode temp = leftChild.RightChild;
leftChild.takeParent(parent);
leftChild.setRightChild(parent);
parent.setLeftChild(temp);
setBalanceAndHeight(parent);
setBalanceAndHeight(temp);
setBalanceAndHeight(leftChild);
if (parent == root)
{
root = leftChild;
}
curNode = leftChild;
}
else
{
Console.WriteLine("fixed in left right rotation");
AVLNode leftRightChild = leftChild.RightChild;
AVLNode temp = leftRightChild.LeftChild;
leftRightChild.takeParent(leftChild);
leftRightChild.setLeftChild(leftChild);
leftRightChild.LeftChild.setRightChild(temp);
setBalanceAndHeight(temp);
setBalanceAndHeight(leftChild);
temp = leftRightChild.RightChild;
leftRightChild.takeParent(parent);
leftRightChild.setRightChild(parent);
parent.setLeftChild(temp);
setBalanceAndHeight(temp);
setBalanceAndHeight(parent);
setBalanceAndHeight(leftRightChild);
if (parent == root)
{
root = leftRightChild;
}
curNode = leftRightChild;
}
}
else
{
AVLNode rightChild = parent.RightChild;
//Check if left subtree heavy, else right subtree heavy
if (rightChild.Balance > 0)
{
Console.WriteLine("fixed in right left rotation");
AVLNode rightLeftChild = rightChild.LeftChild;
AVLNode temp = rightLeftChild.RightChild;
rightLeftChild.takeParent(rightChild);
rightLeftChild.setRightChild(rightChild);
rightLeftChild.RightChild.setLeftChild(temp);
setBalanceAndHeight(temp);
setBalanceAndHeight(rightChild);
temp = rightLeftChild.LeftChild;
rightLeftChild.takeParent(parent);
rightLeftChild.setLeftChild(parent);
parent.setRightChild(temp);
setBalanceAndHeight(temp);
setBalanceAndHeight(parent);
setBalanceAndHeight(rightLeftChild);
if (parent == root)
{
root = rightLeftChild;
}
curNode = rightLeftChild;
}
else
{
Console.WriteLine("fixed in left rotation");
AVLNode temp = rightChild.LeftChild;
rightChild.takeParent(parent);
rightChild.setLeftChild(parent);
parent.setRightChild(temp);
setBalanceAndHeight(parent);
setBalanceAndHeight(temp);
setBalanceAndHeight(rightChild);
if (parent == root)
{
root = rightChild;
}
curNode = rightChild;
}
}
}
}
}