LeetCode: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.

思路：先遍历一遍，得出链表长度，注意k可能大于len令k%=len，将尾节点next指针指向首节点,形成一个环，然后接着跑len-k步，从这里断开，就是要求的结果。

 1 /**
 2  * Definition for singly-linked list.
 3  * struct ListNode {
 4  *     int val;
 5  *     ListNode *next;
 6  *     ListNode(int x) : val(x), next(NULL) {}
 7  * };
 8  */
 9 class Solution {
10 public:
11     ListNode* rotateRight(ListNode* head, int k) {
12         if(head==NULL || k==0) return head;
13         
14         int len=1;
15         ListNode *p=head;
16         while(p->next)
17         {
18             len++;
19             p=p->next;
20         }
21         
22         int step=len-k%len;
23         
24         p->next=head;//尾节点next指针指向首节点
25         //向后走step步 然后断开
26         
27         for(int i=0;i<step;i++)
28             p=p->next;
29         
30         head=p->next;
31         p->next=NULL;
32         
33         return head;
34     }
35 };