Rotate List

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

Example

Given 1->2->3->4->5 and k = 2, return 4->5->1->2->3.

分析：

先得到list size, 然后 k = k % size. 找到新head，然后把tail链接到head.

 /**
  * Definition for singly-linked list.
  * public class ListNode {
  *     int val;
  *     ListNode next;
  *     ListNode(int x) {
  *         val = x;
  *         next = null;
  *     }
  * }
  */
 public class Solution {
     /**
      * @param head: the List
      * @param k: rotate to the right k places
      * @return: the list after rotation
      */
     public ListNode rotateRight(ListNode head, int k) {
         if (head == null || head.next == null) return head;
         // write your code here
         int size = size(head);
         k = k % size;

         if (k == ) return head;
         ListNode pointer = head;
         for (int i = ; i <= size - k - ; i++) {
             pointer = pointer.next;
         }

         ListNode newHead = pointer.next;
         pointer.next = null;

         // link the tail to the head
         ListNode current = newHead;
         while (current.next != null) {
             current = current.next;
         }
         current.next = head;
         return newHead;
     }

     public int size(ListNode head) {
         int count = ;
         while (head != null) {
             count++;
             head = head.next;
         }
         return count;
     }
 }

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