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.

Solution: Notice that k can be larger than the list size (k % list_size).
This solution traverses the list twice at most.

/**
* Definition for singly-linked list.
* struct ListNode {
*     int val;
*     ListNode *next;
*     ListNode(int x) : val(x), next(NULL) {}
* };
*/
class Solution {
public:
ListNode *rotateRight(ListNode *head, int k) {
if(!head) return NULL;
ListNode* tail = head;
int counter = 1;
while(tail->next) {
tail = tail->next;
counter++;
}
k = k % counter; // in case the list rotates more than one round
if(k == 0) return head;

ListNode* cur = head;
for(int i = 0; i < counter - k - 1; i++)
cur = cur->next;

ListNode* newHead = cur->next;
cur->next = NULL;
tail->next = head;

return newHead;
}
};