题解 | #输出单向链表中倒数第k个结点#

满足下面两个要求：

(1)正序构建链表;

(2)构建后要忘记链表长度。

import java.util.Scanner;

/**
 * 【输出单向链表中倒数第k个结点】
 *
 *
 */
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()) {
            int size = sc.nextInt();

            ListNode listNode = new ListNode();
            for (int i = 0; i < size; i++) {
                int value = sc.nextInt();
                listNode.add(value);
            }

            int index = sc.nextInt();
            System.out.println(listNode.get(index));
        }
    }
}

class ListNode {
    // 首节点
    Node first;
    // 尾节点
    Node last;

    /**
     * 新增节点
     * @param value
     */
    public void add(Integer value) {
        Node node = new Node(value, null, null);
        if (first == null) {
            first = node;
            last = node;
            return;
        }

        Node headNode = first;
        while (headNode.getNext() != null) {
            headNode = headNode.getNext();
        }

        headNode.setNext(node);
        node.setHead(headNode);
        last = node;
    }

    /**
     * 根据位置获取节点
     * @param index
     * @return
     */
    public Integer get(Integer index) {
        Node lastNode = last;
        for (int i = 0; i < index - 1; i++) {
            lastNode = lastNode.getHead();
        }
        return lastNode.value;
    }

    private class Node{
        int value;
        // 前节点
        Node head;
        // 后节点
        Node next;

        public Node(int value, Node head, Node next) {
            this.value = value;
            this.head = head;
            this.next = next;
        }

        public int getValue() {
            return value;
        }

        public void setValue(int value) {
            this.value = value;
        }

        public Node getHead() {
            return head;
        }

        public void setHead(Node head) {
            this.head = head;
        }

        public Node getNext() {
            return next;
        }

        public void setNext(Node next) {
            this.next = next;
        }
    }
}