链表中倒数第k个结点

 1 class Solution {
 2 public:
 3     ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {
 4         auto first = pListHead, second = pListHead;
 5         while(k--){
 6             if(first) first = first->next;
 7             else return nullptr;
 8         }
 9         while(first){
10             first = first->next;
11             second = second->next;
12         }
13         return second;
14     }
15 };