programming-examples/java/Graph_Problems_Algorithms/Java Program to Implement Treap.java

/*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.*/

/**
 *  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 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