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) return NULL;        ListNode *cur = head;        int n = 0;        while(cur) {            cur = cur->next;            ++n;        }                        ListNode *slow = head;        ListNode *fast = head;                k %= n;        for (int i = 0; i < k; ++i) {            if (fast) fast = fast->next;        }        if (!fast) return head;                while(fast->next) {            fast = fast->next;            slow = slow->next;        }        fast->next = head;        fast = slow->next;        slow->next = NULL;        return fast;    }};