public class ReversePart {
	public class Node{
		public int value;
		public Node next;
		public Node (int data){
			this.value=data;
		}		
	}
	public Node reversePart(Node head,int from,int to){
		int len=0;
		Node node1=head;
		Node fPre=null;
		Node tPos=null;
		while(node1!=null){
			len++;
			fPre=len==from-1?node1:fPre;
			tPos=len==to+1?node1:tPos;
			node1=node1.next;
		}
		if(from>to||from<1||to>len){
			return head;
		}
		node1=fPre==null?head:fPre.next;
		Node node2=node1.next;
		node1.next=tPos;
		Node next=null;
		while(node2!=tPos){
			next=node2.next;
			node2.next=tPos;
			node1=node2;
			node2=next;
			
		}
		if(fPre!=null){
			fPre.next=node1;
			return head;		
		}
		return node1;	
	}
}