/**
 * @描述     頭尾相接的鏈表
 * @項目名稱   Java_DataStruct
 * @包名     com.struct.linklist
 * @類名     LinkList
 * @author   chenlin
 * @date    2010年6月26日 上午8:00:28
 * @version   1.0
 */
public class FirstLastLinkList {
  //頭
  private Node first;
  //尾
  private Node last;
  public FirstLastLinkList(){
    first = null;
    last = null;
  }
  /**
   * 插入數(shù)據(jù)
   * @param value
   */
  public void insertFirst(long value){
    Node newNode = new Node(value);
    if (first == null) {
      last = newNode;
    }else {
      //把first節(jié)點(diǎn)往下移動
      newNode.next = first;
    }
    //把插入的節(jié)點(diǎn)作為新的節(jié)點(diǎn)
    first = newNode;
  }
  /**
   * 插入數(shù)據(jù)
   * @param value
   */
  public void insertLast(long value){
    Node newNode = new Node(value);
    if (first == null) {
      first = newNode;
    }else {
      last.next = newNode;
    }
    //把最后個節(jié)點(diǎn)設(shè)置為最新的節(jié)點(diǎn)
    last = newNode;
  }
  public boolean isEmpty(){
    return first == null;
  }
  /**
   * 刪除頭節(jié)點(diǎn)
   * @param value
   * @return
   */
  public Node deleteFirst(){
    if (first == null) {
      throw new RuntimeException("鏈表數(shù)據(jù)不存在");
    }
    if (first.next == null) {
      last = null;
    }
    Node temp = first;
    first = temp.next;
    return temp;
  }
  public Node deleteByKey(long key){
    Node current = first;
    Node last = first;
    while(current.data != key){
      if (current.next == null) {
        System.out.println("沒找到節(jié)點(diǎn)");
        return null;
      }
      last = current;
      current = current.next;
    }
    if (current == first) {
      //return deleteFirst();
      //指向下個就表示刪除第一個
      first = first.next;
    }else {
      last.next = current.next;
    }
    return current;
  }
  /**
   * 顯示所有的數(shù)據(jù)
   */
  public void display(){
    if (first == null) {
      //throw new RuntimeException("鏈表數(shù)據(jù)不存在");
      return;
    }
    Node current = first;
    while(current != null){
      current.display();
      current = current.next;
    }
    System.out.println("---------------");
  }
  /**
   * 查找節(jié)點(diǎn)1
   * @param value
   * @return
   */
  public Node findByValue(long value){
    Node current = first;
    while(current != null){
      if (current.data != value) {
        current = current.next;
      }else {
        break;
      }
    }
    if (current == null) {
      System.out.println("沒找到");
      return null;
    }
    return current;
  }
  /**
   * 查找節(jié)點(diǎn)2
   *
   * @param key
   * @return
   */
  public Node findByKey(long key) {
    Node current = first;
    while (current.data != key) {
      if (current.next == null) {
        System.out.println("沒找到");
        return null;
      }
      current = current.next;
    }
    return current;
  }
  /**
   * 根據(jù)索引查找對應(yīng)的值
   * @param position
   * @return
   */
  public Node findByPosition(int position){
    Node current = first;
    //為什么是position - 1，因為要使用遍歷，讓current指向下一個， 所以position - 1的下個node就是要找的值
    for (int i = 0; i < position - 1 ; i++) {
      current = current.next;
    }
    return current;
  }
  public static void main(String[] args) {
    FirstLastLinkList linkList = new FirstLastLinkList();
    linkList.insertFirst(21);
    linkList.insertFirst(22);
    linkList.insertFirst(23);
    linkList.insertLast(24);
    linkList.insertLast(25);
    linkList.insertLast(26);
    linkList.insertLast(27);
    linkList.display();
    System.out.println("---查找-------------------------------------");
    linkList.findByKey(25).display();
    System.out.println("--刪除first-------------------------------------");
    //linkList.deleteFirst().display();
    ///linkList.deleteFirst().display();
    //linkList.deleteFirst().display();
    //linkList.deleteFirst().display();
    System.out.println("-刪除指定值---------------------------------------");
    linkList.deleteByKey(27).display();
    linkList.deleteByKey(21).display();
    System.out.println("----------------------------------------");
    linkList.display();
  }
}