Updates

src/main/java/com/thealgorithms/tree/AVL.java

@@ -0,0 +1,295 @@
+package com.thealgorithms.tree;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+public class AVL {
+
+    private static class Node {
+        int key;
+        int height;
+        Node left;
+        Node right;
+
+        Node(int key) {
+            this.key = key;
+            this.height = 1;
+            this.left = null;
+            this.right = null;
+        }
+    }
+
+    private Node root;
+
+    public AVL() {
+        root = null;
+    }
+
+    public void insert(int key) {
+        root = insertRecursive(root, key);
+    }
+
+    public void delete(int key) {
+        root = deleteRecursive(root, key);
+    }
+
+    public boolean search(int key) {
+        return searchRecursive(root, key);
+    }
+
+    public int findMin() {
+        if (root == null) {
+            throw new NoSuchElementException("AVL Tree is empty");
+        }
+        return findMinNode(root).key;
+    }
+
+    public int findMax() {
+        if (root == null) {
+            throw new NoSuchElementException("AVL Tree is empty");
+        }
+        Node cur = root;
+        while (cur.right != null) {
+            cur = cur.right;
+        }
+        return cur.key;
+    }
+
+    public void printInorder() {
+        System.out.print("Inorder: ");
+        printInorderRecursive(root);
+        System.out.println();
+    }
+
+    public void printPreorder() {
+        System.out.print("Preorder: ");
+        printPreorderRecursive(root);
+        System.out.println();
+    }
+
+    public void printPostorder() {
+        System.out.print("Postorder: ");
+        printPostorderRecursive(root);
+        System.out.println();
+    }
+
+    public List<Integer> inorderList() {
+        List<Integer> res = new ArrayList<>();
+        inorderToList(root, res);
+        return res;
+    }
+
+    public List<Integer> preorderList() {
+        List<Integer> res = new ArrayList<>();
+        preorderToList(root, res);
+        return res;
+    }
+
+    public List<Integer> postorderList() {
+        List<Integer> res = new ArrayList<>();
+        postorderToList(root, res);
+        return res;
+    }
+
+    private Node insertRecursive(Node node, int key) {
+        if (node == null) {
+            return new Node(key);
+        }
+
+        if (key < node.key) {
+            node.left = insertRecursive(node.left, key);
+        } else if (key > node.key) {
+            node.right = insertRecursive(node.right, key);
+        } else {
+            return node;
+        }
+
+        updateHeight(node);
+        return balanceNode(node);
+    }
+
+    private Node deleteRecursive(Node node, int key) {
+        if (node == null) {
+            return null;
+        }
+
+        if (key < node.key) {
+            node.left = deleteRecursive(node.left, key);
+        } else if (key > node.key) {
+            node.right = deleteRecursive(node.right, key);
+        } else {
+            if (node.left == null || node.right == null) {
+                Node temp = null;
+                if (node.left != null) {
+                    temp = node.left;
+                } else {
+                    temp = node.right;
+                }
+
+                if (temp == null) {
+                    node = null;
+                } else {
+                    node = temp;
+                }
+            } else {
+                Node successor = findMinNode(node.right);
+                node.key = successor.key;
+                node.right = deleteRecursive(node.right, successor.key);
+            }
+        }
+
+        if (node == null) {
+            return null;
+        }
+
+        updateHeight(node);
+        return balanceNode(node);
+    }
+
+    private boolean searchRecursive(Node node, int key) {
+        if (node == null) {
+            return false;
+        }
+        if (key == node.key) {
+            return true;
+        }
+        if (key < node.key) {
+            return searchRecursive(node.left, key);
+        } else {
+            return searchRecursive(node.right, key);
+        }
+    }
+
+    private Node findMinNode(Node node) {
+        Node cur = node;
+        while (cur.left != null) {
+            cur = cur.left;
+        }
+        return cur;
+    }
+
+    private Node rightRotate(Node y) {
+        Node x = y.left;
+        Node t2 = x.right;
+
+        x.right = y;
+        y.left = t2;
+
+        updateHeight(y);
+        updateHeight(x);
+
+        return x;
+    }
+
+    private Node leftRotate(Node x) {
+        Node y = x.right;
+        Node t2 = y.left;
+
+        y.left = x;
+        x.right = t2;
+
+        updateHeight(x);
+        updateHeight(y);
+
+        return y;
+    }
+
+    private Node balanceNode(Node node) {
+        int balance = getBalance(node);
+
+        if (balance > 1 && getBalance(node.left) >= 0) {
+            return rightRotate(node);
+        }
+
+        if (balance > 1 && getBalance(node.left) < 0) {
+            node.left = leftRotate(node.left);
+            return rightRotate(node);
+        }
+
+        if (balance < -1 && getBalance(node.right) <= 0) {
+            return leftRotate(node);
+        }
+
+        if (balance < -1 && getBalance(node.right) > 0) {
+            node.right = rightRotate(node.right);
+            return leftRotate(node);
+        }
+
+        return node;
+    }
+
+    private int height(Node node) {
+        if (node == null) {
+            return 0;
+        } else {
+            return node.height;
+        }
+    }
+
+    private void updateHeight(Node node) {
+        node.height = 1 + Math.max(height(node.left), height(node.right));
+    }
+
+    private int getBalance(Node node) {
+        if (node == null) {
+            return 0;
+        } else {
+            return height(node.left) - height(node.right);
+        }
+    }
+
+    private void printInorderRecursive(Node node) {
+        if (node == null) {
+            return;
+        }
+        printInorderRecursive(node.left);
+        System.out.print(node.key + " ");
+        printInorderRecursive(node.right);
+    }
+
+    private void printPreorderRecursive(Node node) {
+        if (node == null) {
+            return;
+        }
+        System.out.print(node.key + " ");
+        printPreorderRecursive(node.left);
+        printPreorderRecursive(node.right);
+    }
+
+    private void printPostorderRecursive(Node node) {
+        if (node == null) {
+            return;
+        }
+        printPostorderRecursive(node.left);
+        printPostorderRecursive(node.right);
+        System.out.print(node.key + " ");
+    }
+
+    private void inorderToList(Node node, List<Integer> out) {
+        if (node == null) {
+            return;
+        }
+        inorderToList(node.left, out);
+        out.add(node.key);
+        inorderToList(node.right, out);
+    }
+
+    private void preorderToList(Node node, List<Integer> out) {
+        if (node == null) {
+            return;
+        }
+        out.add(node.key);
+        preorderToList(node.left, out);
+        preorderToList(node.right, out);
+    }
+
+    private void postorderToList(Node node, List<Integer> out) {
+        if (node == null) {
+            return;
+        }
+        postorderToList(node.left, out);
+        postorderToList(node.right, out);
+        out.add(node.key);
+    }
+}