lintcode:Rotate List

Given a list, rotate the list to the right by k places, where k is non-negative.

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:    /**     * @param head: the list     * @param k: rotate to the right k places     * @return: the list after rotation     */    int ListCount(ListNode* head)    {        if (!head)            return 0;                int count = 1;                ListNode *pCurNode = head;                while (pCurNode->next)        {            pCurNode = pCurNode->next;            count++;        }                return count;    }         ListNode *rotateRight(ListNode *head, int k) {        // write your code here        if (!head)            return NULL;        if (k == 0)            return head;                int nodeCount =  ListCount(head);        if (nodeCount == 1)            return head;                        ListNode* pFastNode = head;        ListNode* pSlowNode = head;                ListNode fakeHead = ListNode(-1);        ListNode* pPreNode  = &fakeHead;        pPreNode->next = head;                k = k%ListCount(head);                for (int i=1; i<=k-1; i++)        {            if (pFastNode->next)            {                pFastNode = pFastNode->next;            }            else            {                return head;            }        }                while (pFastNode->next != NULL)        {            pFastNode = pFastNode->next;            pSlowNode = pSlowNode->next;            pPreNode  = pPreNode->next;        }                pFastNode->next = head;        pPreNode->next = NULL;                return pSlowNode;    }};