JAVA Code:Query Operation In Binary Search Tree (BST)

/* Query operation in BST
*  1>Search
*  2>insert
*  3>delete
*  4>successor
*  5>predecessor
*  6>Tree Minimum
*  7>Tree Maximum
*  8> Tree travelsals- inorder,preorder,levelorder,postorder
***
*author...maulik gohil
*/

import java.util.Scanner;
import java.util.*;
public class Main {
public static void main(String args[])
{
Scanner s=new Scanner(System.in);
Qprocess qp=new Qprocess();

boolean flag=true;

while(flag)
{
System.out.println();
System.out.println("0-exit 1-insert 2-search 3-delete 4-successor 5-predecessor 6-                                                                  maximum 7-minimum");

int n=Integer.parseInt(s.nextLine());
if(n==1)
{
//insert
int entry=Integer.parseInt(s.nextLine());
Node node=new Node(entry);
qp.insert(node);
}
else if(n==2)
{
//search
int entry=Integer.parseInt(s.nextLine());
qp.search(entry);
}
else if(n==3)
{
//delete
int entry=Integer.parseInt(s.nextLine());
qp.delete(entry);
}
else if(n==4)
{
//successor
int entry=Integer.parseInt(s.nextLine());
qp.successor(entry);

}
else if(n==5)
{
//predecessor
 int entry=Integer.parseInt(s.nextLine());
qp.predecessor(entry);
}
else if(n==6)
{
//maximum
qp.maximum();
}
else if(n==7)
{
//minimum
qp.minimum();
}
if(n==0)
{
//termination of loop
flag=false;
}
}
        }
}

public class Qprocess {

public Node root=null;

public void insert(Node node)

{

Node y=null;

Node x=null;

x=root;

while(x!=null)

{

y=x;

if(node.key<x.key)

x=x.left;

else

x=x.right;

}

node.parent=y;

if(y==null)

root=node;

else if(node.key<y.key)

y.left=node;

else

y.right=node;

System.out.print("inorder  "+">> ");

this.Inorder(root); 

System.out.println();

System.out.print("preorder "+">> ");

this.Preorder(root);

System.out.println();

System.out.print("postorder"+">> ");

this.Postorder(root);

System.out.println();

System.out.print("levelorder"+">> ");

this.levelorder(root);

}

private void Inorder(Node x)

{

if(x==null)

return;

this.Inorder(x.left);

System.out.print(" "+x.key);

this.Inorder(x.right);

}

private void Preorder(Node x)

{

if(x==null)

return;

System.out.print(" "+x.key);

this.Preorder(x.left);

this.Preorder(x.right);

}

private void Postorder(Node x)

{

if(x==null)

return;

this.Postorder(x.left);

this.Postorder(x.right);

System.out.print(" "+x.key);

}

private void levelorder(Node x)

{

Queue queue=new LinkedList();

if(x==null)

return;

else

queue.add(x);

while(!queue.isEmpty())

{

Node current=(Node) queue.poll();

System.out.print(" "+current.key);

if(current.left!=null)

queue.add(current.left);

if(current.right!=null)

queue.add(current.right);

}

}

public void search(int x)

{

Node temp=root;

while(temp!=null && temp.key!=x)

{

if(x<temp.key)

temp=temp.left;

else

temp=temp.right;

}

if(temp!=null)

System.out.print(temp.key);

else

System.out.print("not found");

}

public void maximum()

{

Node temp=root;

while(temp.right!=null)

{

temp=temp.right;

}

System.out.print(temp.key);

}

public void minimum()

{

Node temp=root;

while(temp.left!=null)

{

temp=temp.left;

}

System.out.print(temp.key);

}

public void successor(int x) 

{

Node temp=root;

//search method to reach the node where key value match

while(temp!=null && temp.key!=x)

{

if(x<temp.key)

temp=temp.left;

else

temp=temp.right;

}

//successor code

if(temp.right!=null)

{

temp=temp.right;

//treeMIN

while(temp.left!=null)

{

temp=temp.left;

}

System.out.print(temp.key);

}

else

{

Node p=temp.parent;

while(p!=null && p.right==temp)

{

temp=p;

p=p.parent;

}

System.out.print(p.key);

}

}

public void predecessor(int x) 

{

Node temp=root;

//search method to reach the node where key value match

while(temp!=null && temp.key!=x)

{

if(x<temp.key)

temp=temp.left;

else

temp=temp.right;

}

//predecessor code

if(temp.left!=null)

{

temp=temp.left;

//treeMAX

while(temp.right!=null)

{

temp=temp.right;

}

System.out.print(temp.key);

}

else

{

Node p=temp.parent;

while(p!=null && p.left==temp)

{

temp=p;

p=p.parent;

}

System.out.print(p.key);

}

}

        public void delete(int x) 

{

Node t=null;

Node y=null;

Node temp=root;

while(temp!=null && temp.key!=x)

{

if(x<temp.key)

temp=temp.left;

else

temp=temp.right;

}

if(temp.left==null || temp.right==null)//one or no child

{

y=temp;

}

else

{

if(temp.right!=null)

{

temp=temp.right;

//treeMIN

while(temp.left!=null)

{

temp=temp.left;

}

y=temp;

System.out.println(y.key);

System.out.println("check22");

}

else

{

Node p=temp.parent;

while(p!=null && p.right==temp)

{

temp=p;

p=p.parent;

}

y=p;

}

}

if(y.left!=null)

{

t=y.left;

}

else

{

t=y.right;

}

if(t!=null)

{

t.parent=y.parent;

}

if(y.parent==null)

{

root=t;

}

else if(y==y.parent.left)

{

y.parent.left=t;

}

else

{

y.parent.right=t;

}

System.out.print("inorder  "+">> ");

this.Inorder(root); 

System.out.println();

System.out.print("preorder "+">> ");

this.Preorder(root);

System.out.println();

System.out.print("postorder"+">> ");

this.Postorder(root);

System.out.println();

System.out.print("levelorder"+">> ");

this.levelorder(root);

}

}

public class Node 

{

int key;

Node left;

Node right;

Node parent;

public Node(int x)

{

parent=null;

left=null;

right=null;

this.key=x;

}

}