java-algorithms/AVLTreeJava.java at main · ThePimPom/java-algorithms · GitHub

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// AVL tree implementation in Java

// Create node
classNode {
intitem, height;
Nodeleft, right;

Node(intd) {
item = d;
height = 1;
 }
}

// Tree class
classAVLTreeJava {
Noderoot;

intheight(NodeN) {
if (N == null)
return0;
returnN.height;
 }

intmax(inta, intb) {
return (a > b) ? a : b;
 }

NoderightRotate(Nodey) {
Nodex = y.left;
NodeT2 = x.right;
x.right = y;
y.left = T2;
y.height = max(height(y.left), height(y.right)) + 1;
x.height = max(height(x.left), height(x.right)) + 1;
returnx;
 }

NodeleftRotate(Nodex) {
Nodey = x.right;
NodeT2 = y.left;
y.left = x;
x.right = T2;
x.height = max(height(x.left), height(x.right)) + 1;
y.height = max(height(y.left), height(y.right)) + 1;
returny;
 }

// Get balance factor of a node
intgetBalanceFactor(NodeN) {
if (N == null)
return0;
returnheight(N.left) - height(N.right);
 }

// Insert a node
NodeinsertNode(Nodenode, intitem) {

// Find the position and insert the node
if (node == null)
return (newNode(item));
if (item < node.item)
node.left = insertNode(node.left, item);
elseif (item > node.item)
node.right = insertNode(node.right, item);
else
returnnode;

// Update the balance factor of each node
// And, balance the tree
node.height = 1 + max(height(node.left), height(node.right));
intbalanceFactor = getBalanceFactor(node);
if (balanceFactor > 1) {
if (item < node.left.item) {
returnrightRotate(node);
 } elseif (item > node.left.item) {
node.left = leftRotate(node.left);
returnrightRotate(node);
 }
 }
if (balanceFactor < -1) {
if (item > node.right.item) {
returnleftRotate(node);
 } elseif (item < node.right.item) {
node.right = rightRotate(node.right);
returnleftRotate(node);
 }
 }
returnnode;
 }

NodenodeWithMimumValue(Nodenode) {
Nodecurrent = node;
while (current.left != null)
current = current.left;
returncurrent;
 }

// Delete a node
NodedeleteNode(Noderoot, intitem) {

// Find the node to be deleted and remove it
if (root == null)
returnroot;
if (item < root.item)
root.left = deleteNode(root.left, item);
elseif (item > root.item)
root.right = deleteNode(root.right, item);
else {
if ((root.left == null) || (root.right == null)) {
Nodetemp = null;
if (temp == root.left)
temp = root.right;
else
temp = root.left;
if (temp == null) {
temp = root;
root = null;
 } else
root = temp;
 } else {
Nodetemp = nodeWithMimumValue(root.right);
root.item = temp.item;
root.right = deleteNode(root.right, temp.item);
 }
 }
if (root == null)
returnroot;

// Update the balance factor of each node and balance the tree
root.height = max(height(root.left), height(root.right)) + 1;
intbalanceFactor = getBalanceFactor(root);
if (balanceFactor > 1) {
if (getBalanceFactor(root.left) >= 0) {
returnrightRotate(root);
 } else {
root.left = leftRotate(root.left);
returnrightRotate(root);
 }
 }
if (balanceFactor < -1) {
if (getBalanceFactor(root.right) <= 0) {
returnleftRotate(root);
 } else {
root.right = rightRotate(root.right);
returnleftRotate(root);
 }
 }
returnroot;
 }

voidpreOrder(Nodenode) {
if (node != null) {
System.out.print(node.item + " ");
preOrder(node.left);
preOrder(node.right);
 }
 }

// Print the tree
privatevoidprintTree(NodecurrPtr, Stringindent, booleanlast) {
if (currPtr != null) {
System.out.print(indent);
if (last) {
System.out.print("R----");
indent += " ";
 } else {
System.out.print("L----");
indent += "| ";
 }
System.out.println(currPtr.item);
printTree(currPtr.left, indent, false);
printTree(currPtr.right, indent, true);
 }
 }

// Driver code
publicstaticvoidmain(String[] args) {
AVLTreetree = newAVLTree();
tree.root = tree.insertNode(tree.root, 33);
tree.root = tree.insertNode(tree.root, 13);
tree.root = tree.insertNode(tree.root, 53);
tree.root = tree.insertNode(tree.root, 9);
tree.root = tree.insertNode(tree.root, 21);
tree.root = tree.insertNode(tree.root, 61);
tree.root = tree.insertNode(tree.root, 8);
tree.root = tree.insertNode(tree.root, 11);
tree.printTree(tree.root, "", true);
tree.root = tree.deleteNode(tree.root, 13);
System.out.println("After Deletion: ");
tree.printTree(tree.root, "", true);
 }
}