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;    }};