LeetCode（61）——Rotate List

题目：

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.
AC:class Solution {
public ListNode rotateRight(ListNode head, int k) {
if (null == head || null == head.next) {
return head;
}

ListNode dummyNode = new ListNode(-1);
ListNode fastNode = dummyNode;
ListNode endNode = null;
dummyNode.next = head;
int len = 0;
while (null != fastNode.next) {
fastNode = fastNode.next;
len++;
}
endNode = fastNode;

k = k % len;
if (0 == k) {
return head;
}

k = len - k;
fastNode = dummyNode;
while (k > 0) {
fastNode = fastNode.next;
k--;
}

dummyNode.next = fastNode.next;
endNode.next = head;
fastNode.next = null;

return dummyNode.next;
}
}注意k可能会大于链表长度，因此要对长度取余。