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

思路：
把链表连成环，再在特定的位置断开。注意k可能大于链表的长度。

/** * Definition for singly-linked list. * public class ListNode { *     int val; *     ListNode next; *     ListNode(int x) { val = x; } * } */class Solution {    public ListNode rotateRight(ListNode head, int k) {        if (head == null || k == 0) {              return head;          }          int length = 1;          ListNode node = head;          while (node.next != null) {              ++length;              node = node.next;          }          node.next = head;          int m = k % length;          for (int i = 0; i < length - m; ++i) {              node = node.next;          }          head = node.next;          node.next = null;          return head;      }}