61. Rotate List

方法1:

链表首尾相连，将第len个节点的下一个节点设为NULL即可，返回第len＋1个节点

class Solution {public:    ListNode* rotateRight(ListNode* head, int k) {        if(head==NULL||head->next==NULL)            return head;                int len=1;        ListNode* tail=head,*pre=head;        while(tail->next)        {            tail=tail->next;            len++;        }        k=k%len;        k=len-k;        while(k>1)        {            pre=pre->next;            k--;        }        tail->next=head;        head=pre->next;                pre->next=NULL;        return head;    }    };