[LeetCode] 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(k==0 || head==NULL || head->next == NULL)
            return head;
        int len=0;
        ListNode *p = head;
        while(p){
            len++;
            p = p->next;
        }
        while(len<k){
           k -= len;
        }
        ListNode *Pfast = head,*Pslow =head,*h = head;
        int i;
        for(i=0;Pfast!=NULL && i<k+1;i++){
            Pfast = Pfast->next;
        }
        
        while(Pfast!=NULL){
            Pfast = Pfast->next;
            Pslow = Pslow->next;
        }//end while;
        if(Pslow == head && i< k+1)
            return head;
        h = Pslow->next;
        Pslow->next = NULL;
        Pslow = h;
        while(Pslow && Pslow->next)
            Pslow = Pslow->next;
        
       Pslow->next = head;
      return h;
        
    }//end func
};