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Commit bbf6152

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AVL-tree in Java
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‎Trees/avltree/AVLTree.java

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/*
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Copyright (C) Deepali Srivastava - All Rights Reserved
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This code is part of DSA course available on CourseGalaxy.com
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*/
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package avltree;
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public class AVLTree
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{
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private Node root;
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static boolean taller;
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static boolean shorter;
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public AVLTree()
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{
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root = null;
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}
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public boolean isEmpty()
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{
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return (root==null);
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}
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public void display()
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{
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display(root,0);
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System.out.println();
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}
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private void display(Node p,int level)
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{
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int i;
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if(p==null)
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return;
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display(p.rchild, level+1);
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System.out.println();
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for(i=0; i<level; i++)
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System.out.print(" ");
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System.out.print(p.info);
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display(p.lchild, level+1);
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}
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public void inorder()
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{
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inorder(root);
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System.out.println();
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}
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private void inorder(Node p)
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{
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if(p==null )
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return;
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inorder(p.lchild);
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System.out.print(p.info + " ");
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inorder(p.rchild);
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}
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public void insert(int x)
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{
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root = insert(root,x);
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}
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private Node insert(Node p, int x)
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{
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if(p==null)
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{
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p=new Node(x);
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taller = true;
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}
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else if(x < p.info)
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{
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p.lchild = insert(p.lchild,x);
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if(taller==true)
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p = insertionLeftSubtreeCheck(p);
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}
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else if(x > p.info)
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{
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p.rchild = insert(p.rchild,x);
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if(taller==true)
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p = insertionRightSubtreeCheck(p);
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}
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else
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{
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System.out.println(x + " already present in tree");
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taller = false;
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}
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return p;
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}
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private Node insertionLeftSubtreeCheck(Node p)
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{
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switch(p.balance)
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{
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case 0: //Case L_1 : was balanced
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p.balance = 1; // now left heavy
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break;
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case -1: //Case L_2 : was right heavy
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p.balance = 0; // now balanced
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taller = false;
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break;
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case 1: // Case L_3 : was left heavy
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p = insertionLeftBalance(p); //Left Balancing
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taller = false;
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}
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return p;
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}
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private Node insertionRightSubtreeCheck(Node p)
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{
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switch(p.balance)
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{
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case 0: // Case R_1 : was balanced
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p.balance = -1; // now right heavy
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break;
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case 1: // Case R_2 : was left heavy
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p.balance = 0; // now balanced
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taller = false;
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break;
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case -1: // Case R_3: Right heavy
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p = insertionRightBalance(p); // Right Balancing
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taller = false;
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}
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return p;
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}
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private Node insertionLeftBalance(Node p)
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{
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Node a,b;
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a = p.lchild;
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if(a.balance == 1) // Case L_3A : Insertion in AL
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{
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p.balance = 0;
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a.balance = 0;
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p = rotateRight(p);
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}
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else // Case L_3B : Insertion in AR
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{
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b = a.rchild;
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switch(b.balance)
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{
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case 1: // Case L_3B2 : Insertion in BL
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p.balance = -1;
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a.balance = 0;
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break;
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case -1: // Case L_3B2 : Insertion in BR
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p.balance = 0;
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a.balance = 1;
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break;
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case 0: // Case L_3B2 : B is the newly inserted node
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p.balance = 0;
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a.balance = 0;
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}
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b.balance = 0;
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p.lchild = rotateLeft(a);
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p = rotateRight(p);
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}
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return p;
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}
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private Node insertionRightBalance(Node p)
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{
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Node a, b;
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a = p.rchild;
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if(a.balance == -1) // Case R_3A : Insertion in AR
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{
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p.balance = 0;
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a.balance = 0;
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p = rotateLeft(p);
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}
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else // Case R_3B : Insertion in AL
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{
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b = a.lchild;
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switch(b.balance)
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{
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case -1: // Insertion in BR
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p.balance = 1;
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a.balance = 0;
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break;
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case 1: // Insertion in BL
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p.balance = 0;
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a.balance = -1;
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break;
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case 0: // B is the newly inserted node
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p.balance = 0;
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a.balance = 0;
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}
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b.balance = 0;
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p.rchild = rotateRight(a);
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p = rotateLeft(p);
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}
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return p;
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}
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private Node rotateLeft(Node p)
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{
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Node a = p.rchild;
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p.rchild = a.lchild;
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a.lchild = p;
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return a;
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}
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private Node rotateRight(Node p)
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{
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Node a = p.lchild;
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p.lchild = a.rchild;
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a.rchild = p;
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return a;
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}
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public void delete(int x)
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{
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root = delete(root,x);
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}
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private Node delete(Node p, int x)
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{
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Node ch,s;
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if(p==null)
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{
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System.out.println(x + " not found");
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shorter = false;
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return p;
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}
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if(x < p.info) //delete from left subtree
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{
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p.lchild = delete(p.lchild, x);
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if(shorter == true)
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p = deletionLeftSubtreeCheck(p);
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}
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else if(x > p.info) //delete from right subtree
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{
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p.rchild = delete(p.rchild, x);
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if(shorter==true)
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p = deletionRightSubtreeCheck(p);
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}
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else
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{
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//key to be deleted is found
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if( p.lchild!=null && p.rchild!=null ) //2 children
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{
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s=p.rchild;
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while(s.lchild!=null)
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s=s.lchild;
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p.info=s.info;
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p.rchild = delete(p.rchild,s.info);
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if( shorter == true )
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p = deletionRightSubtreeCheck(p);
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}
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else //1 child or no child
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{
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if(p.lchild != null) //only left child
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ch=p.lchild;
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else //only right child or no child
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ch=p.rchild;
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p=ch;
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shorter = true;
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}
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}
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return p;
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}
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private Node deletionLeftSubtreeCheck(Node p)
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{
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switch(p.balance)
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{
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case 0: // Case L_1 : was balanced
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p.balance = -1; // now right heavy
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shorter = false;
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break;
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case 1: // Case L_2 : was left heavy
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p.balance = 0; // now balanced
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break;
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case -1: // Case L_3 : was right heavy
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p = deletionRightBalance(p); //Right Balancing
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}
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return p;
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}
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private Node deletionRightSubtreeCheck(Node p)
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{
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switch(p.balance)
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{
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case 0: // Case R_1 : was balanced
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p.balance = 1; // now left heavy
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shorter = false;
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break;
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case -1: // Case R_2 : was right heavy
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p.balance = 0; // now balanced
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break;
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case 1: // Case R_3 : was left heavy
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p = deletionLeftBalance(p); //Left Balancing
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}
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return p;
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}
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private Node deletionLeftBalance(Node p)
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{
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Node a,b;
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a = p.lchild;
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if( a.balance == 0) // Case R_3A
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{
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a.balance = -1;
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shorter = false;
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p = rotateRight(p);
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}
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else if( a.balance == 1 ) // Case R_3B
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{
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p.balance = 0;
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a.balance = 0;
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p = rotateRight(p);
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}
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else // Case R_3C
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{
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b = a.rchild;
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switch(b.balance)
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{
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case 0: // Case R_3C1
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p.balance = 0;
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a.balance = 0;
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break;
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case -1: // Case R_3C2
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p.balance = 0;
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a.balance = 1;
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break;
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case 1: // Case R_3C3
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p.balance = -1;
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a.balance = 0;
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}
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b.balance = 0;
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p.lchild = rotateLeft(a);
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p = rotateRight(p);
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}
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return p;
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}
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private Node deletionRightBalance(Node p)
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{
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Node a, b;
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a = p.rchild;
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if (a.balance == 0) // Case L_3A
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{
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a.balance = 1;
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shorter = false;
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p = rotateLeft(p);
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}
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else if(a.balance == -1 ) // Case L_3B
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{
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p.balance = 0;
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a.balance = 0;
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p = rotateLeft(p);
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}
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else // Case L_3C
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{
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b = a.lchild;
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switch(b.balance)
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{
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case 0: // Case L_3C1
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p.balance = 0;
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a.balance = 0;
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break;
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case 1: // Case L_3C2
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p.balance = 0;
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a.balance = -1;
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break;
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case -1: // Case L_3C3
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p.balance = 1;
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a.balance = 0;
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}
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b.balance = 0;
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p.rchild = rotateRight(a);
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p = rotateLeft(p);
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}
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return p;
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}
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}

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