Reverse Linked-list in Pairs (Iteration and recursions)

Reverse LinkedList in Pairs:-

Iterative Approach

//1->2->3->4->5->6

public Node reverseTheLinkedListInPairs(Node nd){

Node current = nd;

Node temp=null;

Node head=null;

while(current!=null && current.next!=null){

if(temp!=null)

temp.next.next=current.next; //this step joins 2 to 3 when 3 & 4 exchange happens

temp = current.next;//This takes 2 in temp variable

current.next = temp.next; //this step joins 1 to 3

temp.next=current; //this step join 2 to 1

current=current.next; // this steps makes current as 3

if(head==null)

head=temp;// this is basically maintaining the root

}

return head;

}

Recursive Approach

    public Node reverseTheLinkedListInPairRecursion(Node nd){

    

    if(nd==null || nd.next==null)

    return nd;

    

    Node temp = nd.next;

    nd.next=temp.next;

    temp.next=nd;

    nd.next= reverseTheLinkedListInPairRecursion(nd.next);    

    return temp;

    }