solution.java

import java.io.IOException;
import java.util.Scanner;

public class LinkedListEasy1 {
    //Class for Node
    static class SinglyLinkedListNode {
        public int data;
        public SinglyLinkedListNode next;
        public SinglyLinkedListNode(int nodeData) {
            this.data = nodeData;
            this.next = null;
        }
    }

    //Class for Linked List
    static class SinglyLinkedList {
        public SinglyLinkedListNode head;
        public SinglyLinkedList() {
            this.head = null;
        }

    }

    //Member method to print the data of the nodes of singlyLinkedList
    public static void printSinglyLinkedList(SinglyLinkedListNode node) throws IOException {
        while (node != null) {
            System.out.print(node.data + " -> ");
            node = node.next;
        }
        System.out.println("NULL");
    }


    //Member method to insert node at tail
    static SinglyLinkedListNode insertNodeAtTail(SinglyLinkedListNode head, int data) {
        //Create the node to be inserted in the Linked List
        SinglyLinkedListNode temp = new SinglyLinkedListNode(data);
        //If head is null simply point head to temp and return head
        if (head == null) {
            head = temp;
            return head;
        }
        //If head is not null iterate through the Linked List using a temp Node: curr
        SinglyLinkedListNode curr = head;
        //Exit the while loop when curr.next points to null
        while (curr.next != null) {
            curr = curr.next;
        }
        //Add the temp node at curr.next
        curr.next = temp;
        //Return the head
        return head;
    }

    //Member method to insert Node at Head
    static SinglyLinkedListNode insertNodeAtHead(SinglyLinkedListNode llist, int data) {
        SinglyLinkedListNode temp = new SinglyLinkedListNode(data);
        //If head is null simply point head to temp and return head
        if (llist == null) {
            llist = temp;
            return llist;
        }
        //Point next of the new node created to head
        temp.next = llist;
        //Point head to temp
        llist = temp;
        //Return the head
        return llist;
    }

    //Member method to insert a Node at a specific Position
    static SinglyLinkedListNode insertNodeAtPosition(SinglyLinkedListNode head, int data, int position) {

        SinglyLinkedListNode nodeToInsert = new SinglyLinkedListNode(data);
        //Empty List - Returned newly created node or null
        if (head==null){
            return nodeToInsert;
        }
        //Inserting a Node ahead of the List
        if (position == 0){
            nodeToInsert.next = head;
            return nodeToInsert;
        }
        //Create a copy of Head Node
        SinglyLinkedListNode curr = head;
        //Traverse the Singly Linked List to 1 Position Prior
        //Stop traversing if you reached the end of the List
        int currPosition = 0;
        while (currPosition < position -1 && curr.next != null){
            curr = curr.next;
            currPosition++;
        }
        //Inserting a Node in-between a List or at the end of of a List
        nodeToInsert.next = curr.next;
        curr.next = nodeToInsert;
        return head;
    }

    //Member method to delete a Node at a specific position
    static SinglyLinkedListNode deleteNode(SinglyLinkedListNode head, int position) {
        //Iterate through the list if head is not null
        if(head != null){
            //Create a copy of head
            SinglyLinkedListNode temp;
            temp = head;
            //If position of node to be deleted is 0 simply return head.next
            //that is the element to which head is pointing
            if(position == 0)
                head = head.next;
                //If position is not 1 than iterate to position - 1
            else {
                for(int i=0; i<position-1; i++)
                    temp = temp.next;
                //Now remove the next node by derefrencing it
                // that is pointing the next of current node to next of next of current node
                temp.next = (temp.next).next;
            }
        }
        return head;
    }

    private static final Scanner scanner = new Scanner(System.in);

    public static void main(String[] args) throws IOException {
        //Creating Singly Linked List
        SinglyLinkedList llist = new SinglyLinkedList();
        //Code for adding node at tail of Linked List
        int llistCount = scanner.nextInt();
        for (int i = 0; i < llistCount; i++) {
            int llistItem = scanner.nextInt();
            SinglyLinkedListNode llist_head = insertNodeAtTail(llist.head, llistItem);
            llist.head = llist_head;
        }
        //Code for adding node at head of Linked list
        llistCount = scanner.nextInt();
        for (int i = 0; i < llistCount; i++) {
            int llistItem = scanner.nextInt();
            SinglyLinkedListNode llist_head = insertNodeAtHead(llist.head, llistItem);
            llist.head = llist_head;
        }

        //Code for adding node at a specific position
        int data = scanner.nextInt();
        int position = scanner.nextInt();
        llist.head = insertNodeAtPosition(llist.head, data, position);

        //Code to delete a node at a specific position
        position = scanner.nextInt();
        llist.head = deleteNode(llist.head, position);

        //Call to Method to print out the Linked List
        printSinglyLinkedList(llist.head);
        scanner.close();
    }
}