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Java Program To Implement Red Black Tree Operations.

import java.util.Scanner;
public class RedBlackTreeA {
public static void main(String[] args) {

Scanner scan = new Scanner(System.in);
RBTree rbt = new RBTree(Integer.MIN_VALUE);
char ch;

do {       // Deletion of Nodes is not implemented.
System.out.println("Red Black Tree Operations:");
System.out.println("1. Insert ");
System.out.println("2. Search");
System.out.println("3. Count Nodes");
System.out.println("4. Check Empty");
System.out.println("5. Clear Tree\n");
System.out.print("Enter Your Choice: ");

int choice = scan.nextInt();
switch (choice) {

case 1 :
System.out.print("Enter An Integer To Insert: ");
rbt.insert( scan.nextInt() );
break;

case 2 :
System.out.print("Enter An Integer To Search: ");
System.out.println("Search Result : "+ rbt.search( scan.nextInt() ));
break;

case 3 :
System.out.println("Nodes = "+ rbt.countNodes());
break;

case 4 :
System.out.println("Empty Status = "+ rbt.isEmpty());
break;

case 5 :
System.out.println("Tree Cleared");
rbt.makeEmpty();
break;

default :
System.out.print("Wrong Entry \n ");
break;
}

System.out.print("\nPost Order : ");
rbt.postorder();
System.out.print("\nPre Order : ");
rbt.preorder();
System.out.print("\nIn Order : ");
rbt.inorder();

System.out.println("\n\nDo You Want To Continue (Type Y OR N): ");
ch = scan.next().charAt(0);
} while (ch == 'Y'|| ch == 'y');

scan.close();
}}

RedBlackNode.java:
class RedBlackNode {
RedBlackNode left, right;
int element;
int color;

public RedBlackNode(int theElement){
this( theElement, null, null );
}

public RedBlackNode(int theElement, RedBlackNode lt, RedBlackNode rt){
left = lt;
right = rt;
element = theElement;
color = 1;
}}

class RBTree {
private RedBlackNode current;
private RedBlackNode parent;
private RedBlackNode grand;
private RedBlackNode great;
private RedBlackNode header;
private static RedBlackNode nullNode;

static {
nullNode = new RedBlackNode(0);
nullNode.left = nullNode;
nullNode.right = nullNode;
}

static final int BLACK = 1;
static final int RED   = 0;

public RBTree(int negInf) {
header = new RedBlackNode(negInf);
header.left = nullNode;
header.right = nullNode;
}

public boolean isEmpty() {
return header.right == nullNode;
}

public void makeEmpty() {
header.right = nullNode;
}

public void insert(int item ) {
current = parent = grand = header;
nullNode.element = item;

while (current.element != item) {
great = grand;
grand = parent;
parent = current;

current = item < current.element ? current.left : current.right;
if (current.left.color == RED && current.right.color == RED)
handleReorient( item );
}

if (current != nullNode)
return;
current = new RedBlackNode(item, nullNode, nullNode);

if (item < parent.element)
parent.left = current;

else
parent.right = current;
handleReorient( item );
}

private void handleReorient(int item) {
current.color = RED;
current.left.color = BLACK;
current.right.color = BLACK;

if (parent.color == RED) {
grand.color = RED;

if (item < grand.element != item < parent.element)
parent = rotate( item, grand );  // Start dbl rotate
current = rotate(item, great );
current.color = BLACK;
}

header.right.color = BLACK;
}

private RedBlackNode rotate(int item, RedBlackNode parent){

if(item < parent.element)
return parent.left = item < parent.left.element ? rotateWithLeftChild(parent.left) : rotateWithRightChild(parent.left) ; 

else
return parent.right = item < parent.right.element ? rotateWithLeftChild(parent.right) : rotateWithRightChild(parent.right); 
}

private RedBlackNode rotateWithLeftChild(RedBlackNode k2){
RedBlackNode k1 = k2.left;
k2.left = k1.right;
k1.right = k2;
return k1;
}

private RedBlackNode rotateWithRightChild(RedBlackNode k1){
RedBlackNode k2 = k1.right;
k1.right = k2.left;
k2.left = k1;
return k2;
}

public int countNodes() {
return countNodes(header.right);
}

private int countNodes(RedBlackNode r) {
if (r == nullNode)
return 0;

else {
int l = 1;
l += countNodes(r.left);
l += countNodes(r.right);
return l;
}}

public boolean search(int val) {
return search(header.right, val);
}

private boolean search(RedBlackNode r, int val) {
boolean found = false;

while ((r != nullNode) && !found) {
int rval = r.element;

if (val < rval)
r = r.left;

else if (val > rval)
r = r.right;

else {
found = true;
break;
}

found = search(r, val);
}
return found;
}

public void inorder() {
inorder(header.right);
}

private void inorder(RedBlackNode r) {

if (r != nullNode) {
inorder(r.left);
char c = 'B';

if (r.color == 0)
c = 'R';

System.out.print(r.element +""+c+" ");
inorder(r.right);
}}

public void preorder() {
preorder(header.right);
}

private void preorder(RedBlackNode r) {
if (r != nullNode) {
char c = 'B';

if (r.color == 0)
c = 'R';

System.out.print(r.element +""+c+" ");
preorder(r.left);
preorder(r.right);
}}

public void postorder(){
postorder(header.right);
}

private void postorder(RedBlackNode r) {

if (r != nullNode) {
postorder(r.left);
postorder(r.right);
char c = 'B';

if (r.color == 0)
c = 'R';

System.out.print(r.element +""+c+" ");
}}}
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