[leetcode 61] 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

.

/**
* 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 || !head->next || k == 0) {
return head;
}
ListNode dummy(-1);
auto p = head;
int len = 1;
while (p->next) {
p = p->next;
len++;
}
p->next = head;
k = len - k%len;
for (int i = 0; i < k; i++) {
p = p->next;
}
dummy.next = p->next;
p->next = NULL;
return dummy.next;
}
};