ds-homework/AVL.java at main · ebimoein13/ds-homework · GitHub

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public class AVL {

    class Node {
        int key;
        int bf; // balance factor
        Node left;
        Node right;

        Node(int k) {
            key = k;
            bf = 0;
        }
    }

    Node root;

    public AVL() {
        root = null;
    }

    Node rightRotate(Node y) {
        Node x = y.left;
        Node t2 = x.right;

        x.right = y;
        y.left = t2;

        y.bf = y.bf - 1 - Math.max(x.bf, 0);
        x.bf = x.bf - 1 + Math.min(y.bf, 0);

        return x;
    }

    Node leftRotate(Node x) {
        Node y = x.right;
        Node t2 = y.left;

        y.left = x;
        x.right = t2;

        x.bf = x.bf + 1 - Math.min(y.bf, 0);
        y.bf = y.bf + 1 + Math.max(x.bf, 0);

        return y;
    }

    Node insert(Node node, int key) {
        if (node == null)
            return new Node(key);

        if (key < node.key) {
            node.left = insert(node.left, key);
            node.bf++;
        } else if (key > node.key) {
            node.right = insert(node.right, key);
            node.bf--;
        } else {
            return node;
        }

        if (node.bf == 2) {
            if (node.left.bf >= 0)
                return rightRotate(node);     // LL
            else {
                node.left = leftRotate(node.left); // LR
                return rightRotate(node);
            }
        }

        if (node.bf == -2) {
            if (node.right.bf <= 0)
                return leftRotate(node);     // RR
            else {
                node.right = rightRotate(node.right); // RL
                return leftRotate(node);
            }
        }

        return node;
    }


    Node minValueNode(Node n) {
        while (n.left != null)
            n = n.left;
        return n;
    }

    Node delete(Node node, int key) {
        if (node == null)
            return null;

        if (key < node.key) {
            node.left = delete(node.left, key);
            node.bf--;
        } else if (key > node.key) {
            node.right = delete(node.right, key);
            node.bf++;
        } else {
            if (node.left == null || node.right == null) {
                node = (node.left != null) ? node.left : node.right;
            } else {
                Node temp = minValueNode(node.right);
                node.key = temp.key;
                node.right = delete(node.right, temp.key);
                node.bf++;
            }
        }

        if (node == null)
            return null;


        if (node.bf == 2) {
            if (node.left.bf >= 0)
                return rightRotate(node);
            else {
                node.left = leftRotate(node.left);
                return rightRotate(node);
            }
        }

        if (node.bf == -2) {
            if (node.right.bf <= 0)
                return leftRotate(node);
            else {
                node.right = rightRotate(node.right);
                return leftRotate(node);
            }
        }

        return node;
    }

    void inorder(Node node) {
        if (node != null) {
            inorder(node.left);
            System.out.print(node.key + "(" + node.bf + ") ");
            inorder(node.right);
        }
    }

}