LeetCode -- Rotate List

Question:

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

.

Analysis:

给出一个单链表，旋转链表的从右边数k个位置，将他们按顺序放到左边。k是个非负的整数。

注意一些特殊情况：

如当给出的k值比链表长度还大怎么办？当k=0怎么办？

Answer：

/**
* 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(head == null || head.next == null)
return head;
int len = 0;
ListNode p = head;
ListNode end = null;
while(p != null) {
if(p.next == null)
end = p;
p = p.next;
len++;
}
k %= len;
if(k == 0)
return head;
int pre = len - k;
len = 0;
p = head;
while(len +1 < pre) {
p = p.next;
len++;
}
ListNode q = p.next;
end.next = head;
p.next = null;
return q;
}
}