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:

/**
* 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 || !k) return head;
ListNode *p = head, *q = head;
int num = 0;
while(q && k)
{
q = q->next;
k--;
num++;
}
k %= num;
if(!q && !k) return head;
if(!q) q = head;
while(k--) q = q->next;
while(q->next)
{
p = p->next;
q = q->next;
}
ListNode* r = p->next;
p->next = q->next;
q->next = head;

return r;
}
};