BootCoding-linkedList

Linked list implementation in java

Linked List -

A linked list is a linear collection of data elements, in which linear order is not given by their physical placement in memory. Instead, each element points to the next. It is a data structure consisting of a group of nodes that together represent a sequence.

Consider this example -

node A is the head of the list.
node D is the tail of the list.
Each node is connected in such a way that node A is pointing to node B which in turn pointing to node C.
Node C is again pointing to node D.
Node D is pointing to null as it is the last node of the list.

static class Node
    {
        int data;
        Node next;

        public Node(int data)
        {
            this.data = data;
            this.next = null;
        }
    }

Create a class Node which has two attributes data and next.
Next is a pointer to the next node.

How to create new Linked List ?

public static Node createLinkedList()
    {
        Node firstNode = new Node(10);
        Node secondNode = new Node(20);
        Node thirdNode = new Node(30);
        Node forthNode = new Node(40);

        Node head = firstNode;
        head.next = secondNode;
        secondNode.next = thirdNode;
        thirdNode.next = forthNode;
        forthNode.next = null;
        return head;
    }

Create a createLinkedList() method in that class.
createLinkedList() will add a new node to the list
After that alocatng Starting Points to each nodes (i.e firstNode,secondNode,etc)

How to Print lists of nodes ?

public static void printLinkedList(Node head)
    {
        Node temp = head;
        while (temp != null)
        {
            System.out.println(temp.data);
            temp = temp.next;
        }
    }

Then Create a printLinkedList() method in that class.
printLinkedList() will display the nodes present in the list
Define a node temp (variable) which initially pointng to the head of the list.
Traverse through the list till temp pointng to null.
Display each node by making temp to pointng to node next to it in each iteration

How to Insert first node in list ?

public static Node firstInsert(Node head)
    {
        Node newNode = new Node(70);
        newNode.next=head;
        head=newNode;
        return head;
    }

Then Create a firstInsert() method in that class.
firstInsert() will insert new node to the beginning of the list.
Create a new node.
Make the new node points to the head node.
Then,make the new node as the head node.

How to Insert Last node in list ?

public static void lastInsertNode(Node head)
    {
        Node temp = head;
        Node newNode = new Node(50);
        System.out.println(head);
        while (temp.next != null)
        {
            temp = temp.next;
        }
        temp.next = newNode;
    }

Create a lastInsertNode() method in that class.
lastInsertNode() will insert new node at the ending of the list.
Define a node temp (variable) which initially pointng to the head of the list.
Create a new node.
Traverse through the list till temp pointng to null.
if null then Make the next of temp (variable) points to the newNode.

How to Delete First node in list ?

public static void deleteFirstNode(Node head)
    {
        head = head.next;
        printLinkedList(head);
    }

Create a deleteFirstNode() method in that class.
deleteFirstNode() will delete first node in the list.
Make Next of head as head.
then call printLinkedList(head) method to print updated list of Nodes.

How to Delete Last node in list ?

public static void deleteLastNode(Node head)
    {
        Node temp = head;
        while (temp != null) 
        {
            System.out.println(temp.data);
            if (temp.next.next == null)
            {
                temp.next = null;
            }
            temp = temp.next;
        }
    }

Create a deleteFirstNode() method in that class.
deleteFirstNode() will delete first node in the list.
Define a node temp (variable) which initially pointng to the head of the list.
Traverse through the list till temp pointng to null.
Then cheak next of next element is null if temp.next.next == null condition is true then temp.next pointing to null.
if temp.next.next == null condition is false then temp = temp.next this line will be execute.

Anshul0707/BootCoding-linkedList