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.思路：    不能忽略k大于链表长度的情况形成环，并对长度取余*//** * Definition for singly-linked list. * struct ListNode { *     int val; *     struct ListNode *next; * }; */struct ListNode* rotateRight(struct ListNode* head, int k){if(!head) return head;    struct ListNode *tail=head;struct ListNode *newHead=head;int span=1;while(tail->next){tail=tail->next;span++;}tail->next=head;//形成环if(k%=len){k=len-k;while(k>0){k--;tail=tail->next;}}newHead=tail->next;tail->next=NULL;return newHead;}