61. Rotate List（易错）

k places, where k

For example:

Given ​​1->2->3->4->5->NULL​​ and k = ​​2​​,

return ​​4->5->1->2->3->NULL​​.

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比如说 [1],1这样的数据。

class Solution {
public:
  ListNode* rotateRight(ListNode* head, int k) {
    if (head == NULL||k<=0) return head;

    ListNode* p = head;
    int len = 0;
    while (p){
      p = p->next;
      len++;
    }
    k = k%len;///
    if (k == 0) return head;//
    ListNode* faster = head;
    ListNode* slower = head;

    while (k--){
      faster = faster->next;
    }
    while (faster->next){
      faster = faster->next;
      slower = slower->next;
    }
    ListNode* newHead = slower->next;
    slower->next = NULL;
    faster->next = head;
    return newHead;
  }
};