/*

2.Write a menu driven program to perform the following on a Single Linked List

a.insertion at beginning

b.insertion at end

c.insert a node after a specific node

d.deletion from beginning

e.delete from end

f.delete from a particular position

*/

import java.io.*;

//link

class Link {

public int data;

public Link next;

public Link(int d) {

data = d;

// this.next = null;

}

public void displayLink() {

System.out.println(data);

}

}

class LinkList // linkedlist

{

private Link first;

public LinkList() {

first = null;

}

public boolean isEmpty() {

return (first == null);

}

// Insert link to the first

public void insertFirst(int d) {

Link nl = new Link(d);

nl.next = first;

first = nl;

}

// Insert Link to the end

public void insertLast(int d) {

Link nl = new Link(d);

Link cur = first;

if (isEmpty()) {

first = nl;

nl.next = null;

} else {

while (cur.next != null) {

cur = cur.next;

}

cur.next = nl;

nl.next = null;

}

}

// Insert at the position of a given value.

public void insert(int key, int d) {

Link cur = first;

Link prev = first;

Link newLink = new Link(d);

while (cur.data != key) {

if (cur.next == null) {

System.out.println("Key not Found");

break;

} else {

prev = cur;

cur = cur.next;

}

}

newLink.next = prev.next;

prev.next = newLink;

}

// To delete the first element

public int deleteFirst() {

if (isEmpty()) {

System.out.println("THE LIST IS EMPTY");

}

int temp = first.data;

first = first.next;

return temp;

}

// To delete the last element

public int deleteLast() {

Link cur = first;

Link prev = first;

while (cur.next != null) {

prev = cur;

cur = cur.next;

}

int temp = cur.data;

prev.next = null;

return temp;

}

// delete the link cotaining a key

public Link delete(int key) {

Link cur = first;

Link prev = first;

while (cur.data != key) {

if (cur.next == null) {

System.out.println("Key not Found");

break;

}

else {

prev = cur;

cur = cur.next;

}

}

if (cur == first)

first = first.next;

else

prev.next = cur.next;

return cur;

}

// display all elements

public void displayList() {

Link current = first;

// if list is Empty

if (isEmpty()) {

System.out.println("THE LIST IS EMPTY");

}

while (current != null) {

current.displayLink();

current = current.next;

}

}

}

class singleLinkedlist {

public static void main(String args[]) throws IOException {

int choice, value, z;

LinkList obj;

obj = new LinkList();

do {

System.out.println("SINGLE LINKED LIST");

System.out.println("1.INSERT FIRST");

System.out.println("2.INSERT LAST");

System.out.println("3.INSERT LINK");

System.out.println("4.DELETE FIRST");

System.out.println("5.DELETE LAST");

System.out.println("6.DELETE LINK");

System.out.println("7.DISPLAY ALL");

InputStreamReader read = new InputStreamReader(System.in);

BufferedReader in = new BufferedReader(read);

choice = Integer.parseInt(in.readLine());

switch (choice)

{

case 1:

System.out.println("Enter the data to be inserted");

value = Integer.parseInt(in.readLine());

obj.insertFirst(value);

break;

case 2:

System.out.println("Enter the data to be inserted");

value = Integer.parseInt(in.readLine());

obj.insertLast(value);

break;

case 3:

System.out.println("Enter element to be inserted");

value = Integer.parseInt(in.readLine());

System.out.println("Enter the link list value");

z = Integer.parseInt(in.readLine());

obj.insert(z, value);

break;

case 4:

int d = obj.deleteFirst();

System.out.println(d + " is deleted");

break;

case 5:

int del = obj.deleteLast();

System.out.println(del + " is deleted");

break;

case 6:

System.out.println("Enter the data to be deleted");

value = Integer.parseInt(in.readLine());

obj.delete(value);

System.out.println("Deleted");

break;

case 7:

System.out.println("Display all elements in the Link");

obj.displayList();

break;

default:

System.out.println("INVALID INPUT");

}

} while (choice == 1 || choice == 2 || choice == 3 || choice == 4 || choice == 5 || choice == 6 || choice == 7);

}

}