Rotate List

/**
* 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;
ListNode prehead(0);
prehead.next=head;
ListNode *p=head,*pre;
int length=0;
while(p)
{
length++;
pre=p;
p=p->next;

}
k=k%length;
k=length-k;
while(--k)
{
head=head->next;
}

pre->next=prehead.next;
prehead.next=head->next;
head->next=NULL;
return prehead.next;
}
};

/**
* 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;
ListNode prehead(0);
prehead.next=head;
ListNode *p=head;
int length=0;
while(p->next)
{
length++;
p=p->next;

}
length++;
k=k%length;
k=length-k;
p->next=head;
while(k--)
{
p=p->next;
}

prehead.next=p->next;
p->next=NULL;

return prehead.next;
}
};