题解 | #输出单向链表中倒数第k个结点#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int a = in.nextInt();
            ListNode head = new ListNode(-1);
            ListNode temp = head;
            for(int i = 0;i<a;i++){
                ListNode node = new ListNode(in.nextInt());
                temp.next = node;
                temp = temp.next;
            }
            int k = in.nextInt();
            ListNode result = getKthFromEnd(head.next,k);
            if(result != null){
                System.out.println(result.val);
            }else{
                System.out.println(0);
            }
        }
    }

    //快慢指针
    public static ListNode getKthFromEnd(ListNode head,int k){
        if(head == null) return null;
        ListNode fast = head,slow = head;
        for(int i=0;i<k;i++){
            if(fast == null) return fast;
            fast = fast.next; 
        }
        while(fast !=null){
            fast=fast.next;
            slow = slow.next;
        }
        return slow;
    }


}

class ListNode {
    ListNode next;
    int val;
    ListNode(int val) {
        this.val = val;
        next = null;
    }
}