60. Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

For example:
Given 1->2->3->4->5->NULL and k = 2,
return 4->5->1->2->3->NULL.

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/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) {
 *         val = x;
 *         next = null;
 *     }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int n) {
        
        // check
        if(head == null || head.next == null || n==0)
            return head;
        
        // find the lenth
        ListNode r = head;
        int len=0;
        while(r != null){
            len++;
            r = r.next;
        }
        n = n % len;
    
        // check adjusted n
        if(n==0)    return head;
        
        // find the kth
        ListNode s = head;
        ListNode f = head;
        while(n>0){
            f = f.next;
            n--;
        }
        

        while(f.next != null){
            s = s.next;
            f = f.next;
        }
        
        // rotate
        ListNode newHead = s.next;
        f.next = head;
        s.next = null;
        
        return newHead;
    }
}