ReverseInGrps.java

public class ReverseInGrps {

	public Node reveseGrps(Node head, int k){
		int x = k;
		Node head_next=null;
		Node h = head;
		Node head_prev = null;
		while(h!=null && x>0){
			head_next = h.next;
			h.next = head_prev;
			head_prev = h;
			h = head_next;
			x--;
		}
		if(head_next!=null){
			head.next = reveseGrps(head_next,k);
		}
		return head_prev;
		
	}

	public void display(Node head){
		Node n=head;
		while(n!=null){
			System.out.print("->" + n.data);
			n=n.next;
		}
	}
	public static void main(String[] args) {
		Node head = new Node(1);
		head.next =  new Node(2);
		head.next.next =  new Node(3);
		head.next.next.next =  new Node(4);
		head.next.next.next.next =  new Node(5);
		head.next.next.next.next.next =  new Node(6);
		head.next.next.next.next.next.next =  new Node(7);
		head.next.next.next.next.next.next.next =  new Node(8);
		ReverseInGrps r = new ReverseInGrps();
		Node x = r.reveseGrps(head, 3);
		r.display(x);

	}

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