Sword refers to the reciprocal K-node in the Offer list.

The title description enters a linked list, outputting the penultimate K node in the list. Train of Thought: Method 1: Set 2 pointer p,q.　　　　P moves the K-time first, and then the PQ moves back, p to the end of the list, Q points to the last K-node. Attention://need to consider k=0, and the case of list is emptyMethod 2: Use the stack, first all stack, pop k times, get the countdown k node AC code:

1 /*2 struct ListNode {3 int val;4 struct ListNode *next;5 listnode (int x):6 val (x), Next (NULL) {7     }8 };*/9 classSolution {Ten  Public: Onelistnode* Findkthtotail (listnode* plisthead, unsignedintk) { A         if(k==0|| Plisthead==null)//need to consider k=0, and the case that list is empty -             returnNULL;  -          theListNode *p,*Q; -p=Plisthead; -q=Plisthead; -          +          for(intI=1; i<k;i++)//note the boundary value, starting from 1 -         { +             if(p->next!=NULL) AP=p->Next; at             Else -                 returnNULL; -         } -          -          while(p->next!=NULL) -         { inP=p->Next; -Q=q->Next; to         } +          -         returnQ; the      *     } $};

Sword refers to the reciprocal K-node in the Offer list.