package com.rao.linkList;

/**
 * @author Srao
 * @className LinkList
 * @date 2019/12/3 10:39
 * @package com.rao.linkList
 * @Description
 */
public class LinkList {
    /**
     * 定义节点，下标从1开始
     */
    static class Node{
        public Integer data;
        public Node next;
        public Node(Integer data){
            this.data = data;
        }
    }

    //定义头节点
    public Node head;

    /**
     * 用于初始化一个链表
     * @param head
     */
    public LinkList(Node head) {
        this.head = head;
    }

    public LinkList() {
    }

    //根据 data 查找结点
    public Node findNodeByData(Integer data){
        Node currentNode = head;
        while (currentNode != null && !currentNode.data.equals(data)){
            currentNode = currentNode.next;
        }
        return currentNode;
    }

    //根据 index 查找结点
    public Node findNodeByIndex(int index){
        int num = 1;
        Node currentNode = head;
        while (currentNode != null && index != num){
            currentNode = currentNode.next;
            num++;
        }
        return currentNode;
    }

    //插入元素(指定元素向后插入)
    public void insertNode(int index, Node node){
        if (index == 0){
            node.next = head;
            head = node;
            return;
        }
        Node currentNode = findNodeByIndex(index);
        Node nextNode = currentNode.next;
        currentNode.next = node;
        node.next = nextNode;
    }

    //根据值删除结点
    public void deleteNodeByData(Integer data){
        Node currentNode = head;
        Node preNode = null;
        while (currentNode != null && !currentNode.data.equals(data)){
            preNode = currentNode;
            currentNode = currentNode.next;
        }
        if (preNode == null){//第一个命中
            if (head.next != null){
                head = head.next;
            }else {
                head = null;
            }

        }else if (currentNode == null){//最后一个命中
            preNode.next = null;
        }else {
            preNode.next = currentNode.next;
        }
    }

    public static void main(String[] args) {
        LinkList linkList = new LinkList(new Node(100));
        linkList.insertNode(1, new Node(3));
        linkList.insertNode(1, new Node(4));
        linkList.insertNode(1, new Node(5));//向中间插入
        linkList.insertNode(0, new Node(20));//向头插入
        linkList.insertNode(5, new Node(21));//向尾插入
        System.out.println(linkList.findNodeByIndex(2).data);
        System.out.println(linkList.findNodeByData(5).next.data);
        System.out.println(linkList.findNodeByIndex(6).data);
        linkList.deleteNodeByData(100);//删除中间节点节点
        linkList.deleteNodeByData(20);//删除头节点节点
        linkList.deleteNodeByData(21);//删除尾节点
        System.out.println(linkList.head.data);
    }
}

增加和删除一定要分情况讨论，写完代码之后也要对边界情况进行测试，只要思路理清楚了，写代码不是大问题