basicssll.java

class basicssll {
    public static class Node {
        int data;
        Node next;

        Node(int data) {
            this.data = data;
        }
    }

    public static void display(Node a) {
        Node temp = a;
        if (temp.next == null) {
            System.out.println(temp.data);
            return;
        }
        System.out.print(temp.data + "->");
        display(temp.next);
    }

    public static class LinkedList {
        Node head = null;
        Node tail = null;
        int size=0;

        void insertAtEnd(int val) {
            Node temp = new Node(val);
            if (head == null) {
                head = tail = temp;
                size++;
            } else {
                tail.next = temp;
                tail = temp;
                size++;
            }
        }
        void insertAtFirst(int val){
            Node temp=new Node(val);
            if(head==null && tail==null){
                head=tail=temp;
                size++;
            }else{
                temp.next=head;
                head=temp;
                size++;
            }
        }
        void insertAt(int idx,int val){
            Node temp=new Node(val);
            Node t=head;
            if(idx==0){
                insertAtFirst(val);
                return;
            }
            if(idx==size){
                insertAtEnd(val);
                return;
            }
            if(idx>size || idx<0){
                System.out.println("wrong index");
                return;
            }
            for(int i=1;i<idx;i++){
               t=t.next;
            }
            temp.next=t.next;
            t.next=temp;
        }
        int getAt(int idx){
            Node temp=head;
            if(idx>size||idx<0){
                System.out.println("wrong index ");
                return -1;
            }
            if(idx==0){
                return temp.data;
            }else{
                for(int i=1;i<=idx;i++){
                    temp=temp.next;
                }
            }
             return temp.data;
        }
        void deleteAtIndex(int idx){
            Node temp=head;
            if(idx>size||idx<0){
                System.out.println("wrong index");
                return;
            }
            for(int i=0;i<idx-1;i++){
             temp=temp.next;
            }
            temp.next=temp.next.next;
        }

        void display() {
            Node t = head;
            if (t == null) {
                System.out.println("List is empty!");
                return;
            }

            System.out.print("Linked list: ");
            while (t != null) {
                System.out.print(t.data + " -> ");
                t = t.next;
            }
            System.out.println("null");
        }
    }

    public static void main(String args[]) {
        LinkedList l1 = new LinkedList();
        l1.insertAtEnd(5);
        l1.insertAtEnd(10);
        l1.insertAtEnd(15);
        l1.insertAtFirst(4);
         l1.insertAtFirst(2);
         l1.insertAt(3,00);
         l1.display();
         l1.deleteAtIndex(3);
  
        l1.display(); // should print: Linked list: 5 -> 10 -> 15 -> null
    }
}