Java Program to Implement Treap

This is a Java Program to implement Treap. Treap is a form of binary search tree data structure that maintain a dynamic set of ordered keys and allow binary searches among the keys. After any sequence of insertions and deletions of keys, the shape of the tree is a random variable with the same probability distribution as a random binary tree; in particular, with high probability its height is proportional to the logarithm of the number of keys, so that each search, insertion, or deletion operation takes logarithmic time to perform.

Here is the source code of the Java program to implement Treap. The Java program is successfully compiled and run on a Windows system. The program output is also shown below.

/**
 *  Java Program to Implement Treap
 **/
 
 import java.util.Scanner;
 import java.util.Random;
 
 /** Class TreapNode **/
 class TreapNode
 {
     TreapNode left, right;
     int priority, element;
 
     /** Constructor **/    
     public TreapNode()
     {
         this.element = 0;
         this.left = this;
         this.right = this;
         this.priority = Integer.MAX_VALUE;
     }    
 
     /** Constructor **/    
     public TreapNode(int ele)
     {
         this(ele, null, null);
     } 
 
     /** Constructor **/
     public TreapNode(int ele, TreapNode left, TreapNode right)
     {
         this.element = ele;
         this.left = left;
         this.right = right;
         this.priority = new Random().nextInt( );
     }    
 }
 
 /** Class TreapTree **/
 class TreapTree
 {
     private TreapNode root;
     private static TreapNode nil = new TreapNode();
 
     /** Constructor **/
     public TreapTree()
     {
         root = nil;
     }
 
     /** Function to check if tree is empty **/
     public boolean isEmpty()
     {
         return root == nil;
     }
 
     /** Make the tree logically empty **/
     public void makeEmpty()
     {
         root = nil;
     }
 
     /** Functions to insert data **/
     public void insert(int X)
     {
         root = insert(X, root);
     }
     private TreapNode insert(int X, TreapNode T)
     {
         if (T == nil)
             return new TreapNode(X, nil, nil);
         else if (X < T.element)
         {
             T.left = insert(X, T.left);
             if (T.left.priority < T.priority)
             {
                  TreapNode L = T.left;
                  T.left = L.right;
                  L.right = T;
                  return L;
              }    
         }
         else if (X > T.element)
         {
             T.right = insert(X, T.right);
             if (T.right.priority < T.priority)
             {
                 TreapNode R = T.right;
                  T.right = R.left;
                  R.left = T;
                  return R;
             }
         }
         return T;
     }
 
     /** Functions to count number of nodes **/
     public int countNodes()
     {
         return countNodes(root);
     }
     private int countNodes(TreapNode r)
     {
         if (r == nil)
             return 0;
         else
         {
             int l = 1;
             l += countNodes(r.left);
             l += countNodes(r.right);
             return l;
         }
     }
 
     /** Functions to search for an element **/
     public boolean search(int val)
     {
         return search(root, val);
     }
     private boolean search(TreapNode r, int val)
     {
         boolean found = false;
         while ((r != nil) && !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;
     }
 
     /** Function for inorder traversal **/
     public void inorder()
     {
         inorder(root);
     }
     private void inorder(TreapNode r)
     {
         if (r != nil)
         {
             inorder(r.left);
             System.out.print(r.element +" ");
             inorder(r.right);
         }
     }
 
     /** Function for preorder traversal **/
     public void preorder()
     {
         preorder(root);
     }
     private void preorder(TreapNode r)
     {
         if (r != nil)
         {
             System.out.print(r.element +" ");
             preorder(r.left);             
             preorder(r.right);
         }
     }
 
     /** Function for postorder traversal **/
     public void postorder()
     {
         postorder(root);
     }
     private void postorder(TreapNode r)
     {
         if (r != nil)
         {
             postorder(r.left);             
             postorder(r.right);
             System.out.print(r.element +" ");
         }
     }         
 }
 
/** Class TreapTest **/
public class TreapTest
{
    public static void main(String[] args)
    {            
        Scanner scan = new Scanner(System.in);
        /** Creating object of Treap **/
        TreapTree trpt = new TreapTree(); 
        System.out.println("Treap Test\n");          
        char ch;
        /**  Perform tree operations  **/
        do    
        {
            System.out.println("\nTreap Operations\n");
            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");
 
            int choice = scan.nextInt();            
            switch (choice)
            {
            case 1 : 
                System.out.println("Enter integer element to insert");
                trpt.insert( scan.nextInt() );                     
                break;                          
            case 2 : 
                System.out.println("Enter integer element to search");
                System.out.println("Search result : "+ trpt.search( scan.nextInt() ));
                break;                                          
            case 3 : 
                System.out.println("Nodes = "+ trpt.countNodes());
                break;     
            case 4 : 
                System.out.println("Empty status = "+ trpt.isEmpty());
                break;
            case 5 : 
                System.out.println("\nTreap Cleared");
                trpt.makeEmpty();
                break;            
            default : 
                System.out.println("Wrong Entry \n ");
                break;   
            }
            /**  Display tree  **/ 
            System.out.print("\nPost order : ");
            trpt.postorder();
            System.out.print("\nPre order : ");
            trpt.preorder();    
            System.out.print("\nIn order : ");
            trpt.inorder();
 
            System.out.println("\nDo you want to continue (Type y or n) \n");
            ch = scan.next().charAt(0);                        
        } while (ch == 'Y'|| ch == 'y');               
    }
}

Treap Test
 
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
24
 
Post order : 24
Pre order : 24
In order : 24
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
6
 
Post order : 6 24
Pre order : 24 6
In order : 6 24
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
94
 
Post order : 6 94 24
Pre order : 24 6 94
In order : 6 24 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
19
 
Post order : 6 94 24 19
Pre order : 19 6 24 94
In order : 6 19 24 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
28
 
Post order : 6 24 19 94 28
Pre order : 28 19 6 24 94
In order : 6 19 24 28 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
5
 
Post order : 6 5 24 19 94 28
Pre order : 28 19 5 6 24 94
In order : 5 6 19 24 28 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
1
Enter integer element to insert
63
 
Post order : 6 5 24 19 28 94 63
Pre order : 63 28 19 5 6 24 94
In order : 5 6 19 24 28 63 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
2
Enter integer element to search
24
Search result : true
 
Post order : 6 5 24 19 28 94 63
Pre order : 63 28 19 5 6 24 94
In order : 5 6 19 24 28 63 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
3
Nodes = 7
 
Post order : 6 5 24 19 28 94 63
Pre order : 63 28 19 5 6 24 94
In order : 5 6 19 24 28 63 94
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
5
 
Treap Cleared
 
Post order :
Pre order :
In order :
Do you want to continue (Type y or n)
 
y
 
Treap Operations
 
1. insert
2. search
3. count nodes
4. check empty
5. clear
4
Empty status = true
 
Post order :
Pre order :
In order :
Do you want to continue (Type y or n)
 
n