题解 | #输出单向链表中倒数第k个结点#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner fzhinput = new Scanner(System.in);
        while(fzhinput.hasNext()){
            int jdnum = fzhinput.nextInt();
            ListNode head = null; 
            ListNode tail = null;
            for(int i=0;i<jdnum;i++){
                int value = fzhinput.nextInt();
                ListNode lbsz = new ListNode(value);
                if (head == null) {
                    head = lbsz;
                    tail = lbsz;
                } else {
                    tail.zzhen = lbsz;
                    tail = lbsz;
                }
            }
            int k = fzhinput.nextInt();
            ListNode result = findKToTail(head,k);
            if(result!=null){
                System.out.println(result.zkey);
            }
            else{
                System.out.println("null");
            }
        }
    }
    public static ListNode findKToTail(ListNode head,int k){
        if(head==null||k<=0){
            return null;
        }
        ListNode fast = head;
        ListNode slow = head;
        for(int i=0;i<k;i++){
            if(fast!=null){
                fast=fast.zzhen;
            }
            else{
                return null;
            }
        }

        while(fast!=null){
            fast=fast.zzhen;
            slow=slow.zzhen;
        }
        return slow;
    }
    
}
class ListNode{
        int zkey;
        ListNode zzhen;
        ListNode(int z){
            zkey=z;
            zzhen=null;
        }

    }