LinkedLists Algorithms

How to Append a Node at the head of LinkedList?

public class MyLinkedList {
	public static void main(String[] args) {
		Node a = new Node(1);
		Node b = new Node(2);
		Node c = new Node(3);
		a.next=b;
		b.next=c;
		a.printList();
		System.out.println("After adding new node");
		Node newNode = appendANodeAtHead(a,4);
		newNode.printList();
		
}
private static Node appendANodeAtHead(Node head, int data){
	Node newNode = new Node(data);
	newNode.next= head;
	return newNode;
}
static class Node{
	Node next;
	int data;
	Node(int d){
	this.data=d;
	}
	public void printList(){
	Node current=this;
	while(current!=null){
		System.out.println(current.data+"->");
		current = current.next;
		}
		System.out.println();
			
	}
}

How to Append a Node at the tail of LinkedList?

private static Node appendANodeAtTail(Node head, int data){
	Node current = head;
	while(head.next !=null){
		head = head.next;
	}
	head.next=new Node(data);;
	return current;
	}

How to reverse a LinkedList?

private static Node reverse(Node head){
	Node reverseList = head;
	Node list_todo = head.next;
	reverseList.next=null;
	while(list_todo !=null){
		Node temp = list_todo;
		list_todo= list_todo.next;
		temp.next=reverseList;
		reverseList=temp;
	}
	return reverseList;
	}

How to delete a Node from a LinkedList?

private static Node deleteANode(Node head){
	Node current = head;
	if(current == null) return null;
	if(current == head){
		return current.next;
	}
	return current;
	}

How to find out if a linked list is circular or not?

private static boolean circularLinkList(Node head){
   Node slow=head;
   Node fast=head.next;
   while(true){
     if(fast == slow || fast.next==slow){
    	 System.out.println("its circular");
       return true;
     }else{
       fast = fast.next.next;
       slow = slow.next;
     }    
     if(fast == null || fast.next==null){
    	 System.out.println("its not circular");
       return false;
     }    
   }  

 }

How to remove duplicate nodes from a LinkedList?

private static Node removeDupNodes(Node head){
    Node current = head;
    Set mySet = new HashSet();
    mySet.add(current.data);
    while(current.next!=null){
      if(!mySet.contains(current.next.data)){
         mySet.add(current.next.data);
         current = current.next;
      }else{
         current.next = current.next.next;
       }
    }
    return head;  
}

Adding 2 nodes

private static Node addTwoNodes(Node n1, Node n2, int carry){
     if(n1 == null || n2 == null || carry == 0) return null;
	Node result = new Node(carry);
	int value = carry;
	if(n1 != null){
		value +=n1.data;
	}
	if(n2 !=null){
		value +=n2.data;
	}
	result.data=value%10;
	if(n1 != null || n2 != null || value > 10){
	Node more = addTwoNodes(n1 == null ? null : n1.next, n2 == null ? null : n2.next, value >=10 ? 1: 0);
	result.next=more;
	}
		
	return result;
	}