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==NULL||head->next==NULL||k==0)
        return head;
    ListNode *pre0=head ,*pre1, *pre2;
    int len=0;
    while (pre0)
    {
        len++;
        pre1=pre0;
        pre0=pre0->next;
    }
    k%=len;
    if(k==0)return head;
    ListNode  *headNew;
    pre2=head;
    for(int i=0;i<len-k-1;i++)
    {
        pre2=pre2->next;
    }
    headNew=pre2->next;
    pre2->next=NULL;
    pre1->next=head;
    return headNew;
}
/**
ListNode *rotateRight(ListNode *head, int k) 
{
    if(head==NULL||head->next==NULL||k==0)
        return head;
    ListNode *pre0=head;
    int len=0;
    while (pre0)
    {
        len++;
        pre0=pre0->next;
    }
    k%=len;
    if(k==0)return head;
    ListNode *pre1=head, *cur, *headNew;
    int icount=0;
    while(pre1)
    {
        icount++;
        pre1=pre1->next;
        if (icount==k)
        {        
            cur=head;
            while(pre1->next)
            {
                pre1=pre1->next;
                cur=cur->next;
            }
            headNew=cur->next;            
            cur->next=NULL;
            pre1->next=head;    
            return headNew;
        }
    }
}
*/
};