Java Program to Implement Pagoda

This is a Java Program to implement Pagoda. A pagoda is a priority queue implemented with a variant of a binary tree. The root points to its children, as in a binary tree. Every other node points back to its parent and down to its leftmost (if it is a right child) or rightmost (if it is a left child) descendant leaf. The basic operation is merge or meld, which maintains the heap property. An element is inserted by merging it as a singleton. The root is removed by merging its right and left children. Merging is bottom-up, merging the leftmost edge of one with the rightmost edge of the other.

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

/*
 *    Java Program to Implement Pagoda
 */
  
import java.util.Scanner;
  
/* Class PNode */
class PNode
{
    PNode left, right;
    int data;
  
    /* Constructor */
    public PNode(int val)
    {
        data = val;
        left = null;
        right = null;
    }
}
  
/* Class Pagoda */
class Pagoda
{
    private PNode root;
  
    /* Constructor */
    public Pagoda()
    {
        root = null;
    }
    /* Function to check if empty */
    public boolean isEmpty()
    {
        return root == null;
    }
    /* Function to clear */
    public void makeEmpty()
    {
        root = null;
    }
    /* Function to insert value */
    public void insert(int val)
    {
        PNode newNode = new PNode(val);
        root = insert(newNode, root);
    }
    private PNode insert(PNode newNode, PNode pq)
    {
        newNode.left = newNode;
        newNode.right = newNode;
        return (merge(pq, newNode));
    }
    /* Function to merge two nodes */
    private PNode merge(PNode a, PNode b)
    {
        PNode bota, botb, r, temp;
        if (a == null)
            return b;
        else if (b == null)
            return a;
        else
        {
            bota = a.right;    a.right = null;
            /* bottom of b's leftmost edge */
            botb = b.left;    b.left = null;
            r = null;
            /* Merging loop */
            while ( bota != null && botb != null )
                if ( bota.data < botb.data ) 
                {
                    temp = bota.right;
                    if ( r == null )
                        bota.right = bota;
                    else
                    {
                        bota.right = r.right;
                        r.right = bota;
                    }
                    r = bota;
                    bota = temp;
                }
                else
                {
                    temp = botb.left;
                    if ( r == null )
                        botb.left = botb;
                    else
                    {
                        botb.left = r.left;
                        r.left = botb;
                    }
                    r = botb;
                    botb = temp;
                }
            /* one edge is exhausted, finish merge */
            if ( botb == null )
            {
                a.right = r.right;
                r.right = bota;
                return( a );
            }
            else
            {
                b.left = r.left;
                r.left = botb;
                return( b );
            }
        }
    }
    /* Function to delete */
    public void delete()
    {
        root = delete(root);
    }
    private PNode delete(PNode pq)
    {
        PNode le, ri;
        /* Deletion on empty queue */
        if ( pq == null ) 
        {
            System.out.println("Empty");
            return null;
        } 
        else
        {
            /* Find left descendant of root */
            if ( pq.left == pq ) 
                le = null;
            else
            {
                le = pq.left;
                while ( le.left != pq ) 
                    le = le.left;
                le.left = pq.left;
            }
            /* Find right descendant of root */
            if ( pq.right == pq ) 
                ri = null;
            else
            {
                ri = pq.right;
                while ( ri.right != pq ) 
                    ri = ri.right;
                ri.right = pq.right;
            }
            /* merge them */
            return merge(le, ri);
        }        
    }
    /* Function to print root value */
    public void printPagodaRoot()
    {
        if (root != null)
            System.out.print(root.data +"\n");
        else
            System.out.print("Empty\n");
    }    
}
  
  
/* Class PagodaTest */
 public class PagodaTest
 {
     public static void main(String[] args)
     {            
        Scanner scan = new Scanner(System.in);
        /* Creating object of Pagoda */
        Pagoda pgda = new Pagoda(); 
        System.out.println("Pagoda Test\n");          
        char ch;
        /*  Perform tree operations  */
        do   
        {
            System.out.println("\nPagoda Operations\n");
            System.out.println("1. insert ");
            System.out.println("2. delete"); 
            System.out.println("3. check empty");
            System.out.println("4. clear");
  
            int choice = scan.nextInt();            
            switch (choice)
            {
            case 1 : 
                System.out.println("Enter integer element to insert");
                pgda.insert( scan.nextInt() );                     
                break;                          
            case 2 : 
                pgda.delete(); 
                break;                          
            case 3 :
                System.out.println("Empty status = "+ pgda.isEmpty());
                break;
            case 4 : 
                System.out.println("\nCleared");
                pgda.makeEmpty();
                break;            
            default : 
                System.out.println("Wrong Entry \n ");
                break;   
            }
            /*  Display tree  */
  
            System.out.print("\nRoot Element : ");
            pgda.printPagodaRoot();
  
            System.out.println("\nDo you want to continue (Type y or n) \n");
            ch = scan.next().charAt(0);                        
        } while (ch == 'Y'|| ch == 'y');               
     }
 }

Pagoda Test
  
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
45
  
Root Element : 45
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
23
  
Root Element : 45
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
57
  
Root Element : 57
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
19
  
Root Element : 57
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
24
  
Root Element : 57
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
93
  
Root Element : 93
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
1
Enter integer element to insert
87
  
Root Element : 93
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 87
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 57
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 45
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 24
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 23
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : 19
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
2
  
Root Element : Empty
  
Do you want to continue (Type y or n)
  
y
  
Pagoda Operations
  
1. insert
2. delete
3. check empty
4. clear
3
Empty status = true
  
Root Element : Empty
  
Do you want to continue (Type y or n)
  
n