题解 | #输出单向链表中倒数第k个结点# 快慢双指针

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);
        while (in.hasNext()) {
            int inputN = in.nextInt();
            ListNode inputHead = new ListNode(in.nextInt());
            ListNode tmp = inputHead;
            for (int i = 1; i < inputN; i++) {
                inputHead.next = new ListNode(in.nextInt());
                inputHead = inputHead.next;
            }
            int k = in.nextInt();
            System.out.println(daoshu(tmp, k).val);
        }
    }

    public static class ListNode {
        int val;
        ListNode next;

        ListNode() {
        }

        ListNode(int val) {
            this.val = val;
        }

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

    private static ListNode daoshu(ListNode head, int k) {
        if (head == null || head.next == null) {
            return head;
        }
        ListNode dummy = new ListNode(-1);
        ListNode fastHead = head;
        ListNode slowHead = head;

        while (k > 0) {
            fastHead = fastHead.next;
            k--;
        }

        while (fastHead != null && fastHead.next != null) {
            slowHead = slowHead.next;
            fastHead = fastHead.next;
        }

        return slowHead.next;
    }
}