题解 | #输出单向链表中倒数第k个结点#

import java.util.*;

public class Main {

private int size; 
private ListNode head;

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

public Main(int size, int[] array) {
    this.size = size;
    this.head = new ListNode(array[0]);

    ListNode p = head;
    for (int i = 1; i < size; i++) {
        p.next = new ListNode(array[i]);
        p = p.next;
    }
}

public ListNode findKthToTail(int k) {
    // 题目没有指出，无法理解
    if (k == 0) return new ListNode(0);
    if (k < 0 || k > size) return null;
    k = size - k;
    ListNode p = head;
    while (k != 0) {
        p = p.next;
        k--;
    }
    return p;
}

public static void main(String[] args) {
    Scanner in = new Scanner(System.in);
    while (in.hasNext()) {
        int n = Integer.parseInt(in.next());
        int[] array = new int[n];
        for (int i = 0; i < n; i++) {
            array[i] = Integer.parseInt(in.next());
        }
        int k = Integer.parseInt(in.next());
        Main solution = new Main(n, array);
        ListNode node = solution.findKthToTail(k);
        if (node != null) {
            System.out.println(node.val);
        }
        else {
            System.out.println();
        }
    }
} 

}