[LeetCode] 61. 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.

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
public class Solution {
    public ListNode rotateRight(ListNode head, int k) {
    
        if(null == head)
            return null;
        
        if(0 == k)
            return head;
        
        int len = 1;
        
        ListNode tail = head;
        while(null != tail.next){
            tail = tail.next;
            ++len;
        }
        
        tail.next = head;
        
        ListNode c = tail;
        
        k %= len;
        k = len - k;
        
        while(k-- > 0){
            c = c.next;
        }
        
       ListNode ret = c.next;
        c.next = null;
        
        return ret;
        
    }
}