rotateList.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
import java.util.*;
class Solution {
    public ListNode rotateRight(ListNode head, int k) {
        if(head == null || head.next == null){
            return head;
        }
       int length = 1;
       ListNode temp = head;

       while(temp.next != null){
        temp = temp.next;
        length++;
       }
       k %= length;
       if(k == 0){
        return head;
       }

       ListNode curr = head;
       for(int i = 0; i < length - k - 1; i++){
        curr = curr.next;
       }
       ListNode newHead = curr.next;
       curr.next = null;
       temp.next = head;
       return newHead;
    }
}