Java Program to Implement Leftist Heap

// Java Program to Implement Leftist Heap

// Declare all libraries
import java.io.*;
import java.util.Scanner;

// Class Node
class Node {
  
    // elements, and sValue are the variables in class Node
    int element, sValue;
  
    // class has two parameters
    Node left, right;

    public Node(int element) { this(element, null, null); }

    // Function Node where we are using this keyword
    // Which will help us to avoid confusion if we are having
    // same elements

    public Node(int element, Node left, Node right)
    {
        this.element = element;
        this.left = left;
        this.right = right;
        this.sValue = 0;
    }
}

// Class Left heap
class LeftHeap {
  
    // Now parameter is created named head.
    private Node head;

    // Its constructor is created named left heap
    // Returns null
    public LeftHeap() { head = null; }

    // Now we will write function to check if the list is
    // empty
    public boolean isEmpty()
    {
        // If head is null returns true
        return head == null;
    }
  
    // Now we will write a function clear
    public void clear()
    {
        // We will put head is null
        head = null;
    }

    // Now let us create a function merge which will
    // help us merge
    public void merge(LeftHeap rhs)
    {
        // If the present function is rhs
        // then we return it
        if (this == rhs)
            return;
      
        // Here we call the function merge
        // And make rhs is equal to null
        head = merge(head, rhs.head);
        rhs.head = null;
    }

    // Function merge with two Nodes a and b
    public Node merge(Node a, Node b)
    {
        // If A is null
        // We return b
        if (a == null)
            return b;
      
        // If b is null
        // we return A
        if (b == null)
            return a;

        // If we put a element greater than b element
        if (a.element > b.element) {
          
            // We write the swap code
            Node temp = a;
            a = b;
            b = temp;
        }

        // Now we call the function merge to merge a and b
        a.right = merge(a.right, b);
      
        // If a is null we swap right with left and empty
        // right
        if (a.left == null) {
            a.left = a.right;
            a.right = null;
        }
      
        // else
        // if value in a is less than the svalue of right
        // If the condition is satisfied , we swap the left
        // with right
        else {
          
            if (a.left.sValue < a.right.sValue) {
                Node temp = a.left;
                a.left = a.right;
                a.right = temp;
            }
          
            // we store the value in a s Value of right
            // SValue
            a.sValue = a.right.sValue + 1;
        }
      
        // We now return the value of a
        return a;
    }

    // Function insert
    public void insert(int a)
    {
        // This root will help us insert a new variable
        head = merge(new Node(a), head);
    }
  
    // The below function will help us delete minimum
    // function present in the Heap
    public int del()
    {
        // If is empty return -1
        if (isEmpty())
            return -1;

        // Now we will store the element in variable and
        // Call the merge function to del that is converging
        // to head then  we return min
        int min = head.element;
      
        head = merge(head.left, head.right);
        return min;
    }

    // Function order
    // will print the starting and ending points in order.
    public void order()
    {
        order(head);
        System.out.println();
    }

    // Function order with Node r
    // If r not equal to r
    // It prints all the elements iterating from order left
    // to right
    private void order(Node r)
    {
        if (r != null) {
            order(r.left);
            System.out.print(r.element + " ");
            order(r.right);
        }
    }
}

// Class gfg

class GFG {
    public static void main(String[] args)
    {

        // Creating the scanner object
        Scanner sc = new Scanner(System.in);
        System.out.println("LEFTIST HEAP");
      
        // Creating object for class LeftHeap
        LeftHeap h = new LeftHeap();
      
        // Char ch
        char ch;
      
        // Now taking the loop
        do {
            // Now writing down all the functions
            System.out.println("Functions to do");
            System.out.println("1. insert");
            System.out.println("2. delete min");
            System.out.println("3. check empty");
            System.out.println("4. clear");

            // Scanning the choice to be used in switch
            int choice = sc.nextInt();

            // Using switch
            switch (choice) {
                
                // Case 1
                // to insert the elements in the heap
                // call the insert func
            case 1:
                System.out.println("Enter integer element to insert");
                h.insert(sc.nextInt());
                break;
                
                // Delete the minimum element in the func
                
            case 2:
                h.del();
                
                break;
                // To check the empty status of the heap
            case 3:
                System.out.println("Empty status = "
                                   + h.isEmpty());
                break;
                
                // Cleaning the heap
            case 4:
                h.clear();
                break;
                
            default:
                System.out.println("Wrong entry");
                break;
            }
          
            // Prints the inorder traversal
            // Calling the func
            System.out.print("\n Inorder Traversal: ");
            h.order();
          
            // Whether to continue or not
            System.out.println("\n If you wish to continue type Y or y");
          
            ch = sc.next().charAt(0);
        }
      
        // Closing of loop
        while (ch == 'Y' || ch == 'y');
    }
}