package com.tyxh.link;
//节点类
public class Node {
     protected Node next; //指针域
     protected int data;//数据域
    
     public Node( int data) {
           this. data = data;
     }
    
     //显示此节点
     public void display() {
          System. out.print( data + " ");
     }
}

package com.tyxh.link;
//单链表
public class LinkList {
     public Node first; // 定义一个头结点
     private int pos = 0;// 节点的位置

     public LinkList() {
           this. first = null;
     }

     // 插入一个头节点
     public void addFirstNode( int data) {
          Node node = new Node(data);
          node. next = first;
           first = node;
     }

     // 删除一个头结点,并返回头结点
     public Node deleteFirstNode() {
          Node tempNode = first;
           first = tempNode. next;
           return tempNode;
     }

     // 在任意位置插入节点 在index的后面插入
     public void add(int index, int data) {
          Node node = new Node(data);
          Node current = first;
          Node previous = first;
           while ( pos != index) {
              previous = current;
              current = current. next;
               pos++;
          }
          node. next = current;
          previous. next = node;
           pos = 0;
     }

     // 删除任意位置的节点
     public Node deleteByPos( int index) {
          Node current = first;
          Node previous = first;
           while ( pos != index) {
               pos++;
              previous = current;
              current = current. next;
          }
           if(current == first) {
               first = first. next;
          } else {
               pos = 0;
              previous. next = current. next;
          }
           return current;
     }

     // 根据节点的data删除节点(仅仅删除第一个)
     public Node deleteByData( int data) {
          Node current = first;
          Node previous = first; //记住上一个节点
           while (current. data != data) {
               if (current. next == null) {
                    return null;
              }
              previous = current;
              current = current. next;
          }
           if(current == first) {
               first = first. next;
          } else {
              previous. next = current. next;
          }
           return current;
     }

     // 显示出所有的节点信息
     public void displayAllNodes() {
          Node current = first;
           while (current != null) {
              current.display();
              current = current. next;
          }
          System. out.println();
     }

     // 根据位置查找节点信息
     public Node findByPos( int index) {
          Node current = first;
           if ( pos != index) {
              current = current. next;
               pos++;
          }
           return current;
     }

     // 根据数据查找节点信息
     public Node findByData( int data) {
          Node current = first;
           while (current. data != data) {
               if (current. next == null)
                    return null;
              current = current. next;
          }
           return current;
     }
}

package com.tyxh.link;
//测试类
public class TestLinkList {
     public static void main(String[] args) {
          LinkList linkList = new LinkList();
          linkList.addFirstNode(20);
          linkList.addFirstNode(21);
          linkList.addFirstNode(19);
           //19,21,20
          linkList.add(1, 22); //19,22,21,20
          linkList.add(2, 23); //19,22,23,21,20
          linkList.add(3, 99); //19,22,23,99,21,20
          linkList.displayAllNodes();
//        Node node = linkList.deleteFirstNode();
//        System.out.println("node : " + node.data);
//        linkList.displayAllNodes();
//        node = linkList.deleteByPos(2);
//        System.out.println("node : " + node.data);
//        linkList.displayAllNodes();
//        linkList.deleteFirstNode();
          Node node = linkList.deleteByData(19);
//        Node node = linkList.deleteByPos(0);
          System. out.println( "node : " + node. data);
          linkList.displayAllNodes();
          Node node1 = linkList.findByPos(0);
          System. out.println( "node1: " + node1. data);
          Node node2 = linkList.findByData(22);
          System. out.println( "node2: " + node2. data);
     }
}