Java 数据结构之双端链表

一、概述：

二、具体实现

/**
* @描述         头尾相接的链表
* @项目名称      Java_DataStruct
* @包名         com.struct.linklist
* @类名         LinkList
* @author      chenlin
* @date        2010年6月26日 上午8:00:28
* @version     1.0
*/

public class FirstLastLinkList {

//头
private Node first;
//尾
private Node last;

public FirstLastLinkList(){
first = null;
last = null;
}

/**
* 插入数据
* @param value
*/
public void insertFirst(long value){
Node newNode = new Node(value);
if (first == null) {
last = newNode;
}else {
//把first节点往下移动
newNode.next = first;
}
//把插入的节点作为新的节点
first = newNode;
}

/**
* 插入数据
* @param value
*/
public void insertLast(long value){
Node newNode = new Node(value);
if (first == null) {
first = newNode;
}else {
last.next = newNode;
}
//把最后个节点设置为最新的节点
last = newNode;
}

public boolean isEmpty(){
return first == null;
}

/**
* 删除头节点
* @param value
* @return
*/
public Node deleteFirst(){
if (first == null) {
throw new RuntimeException("链表数据不存在");
}
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("没找到节点");
return null;
}
last = current;
current = current.next;
}
if (current == first) {
//return deleteFirst();
//指向下个就表示删除第一个
first = first.next;
}else {
last.next = current.next;
}
return current;
}

/**
* 显示所有的数据
*/
public void display(){
if (first == null) {
//throw new RuntimeException("链表数据不存在");
return;
}
Node current = first;
while(current != null){
current.display();
current = current.next;
}
System.out.println("---------------");
}

/**
* 查找节点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("没找到");
return null;
}
return current;
}

/**
* 查找节点2
*
* @param key
* @return
*/
public Node findByKey(long key) {
Node current = first;
while (current.data != key) {
if (current.next == null) {
System.out.println("没找到");
return null;
}
current = current.next;
}
return current;
}

/**
* 根据索引查找对应的值
* @param position
* @return
*/
public Node findByPosition(int position){
Node current = first;
//为什么是position - 1，因为要使用遍历，让current指向下一个， 所以position - 1的下个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("--删除first-------------------------------------");

//linkList.deleteFirst().display();
///linkList.deleteFirst().display();
//linkList.deleteFirst().display();
//linkList.deleteFirst().display();

System.out.println("-删除指定值---------------------------------------");
linkList.deleteByKey(27).display();
linkList.deleteByKey(21).display();

System.out.println("----------------------------------------");
linkList.display();

}
}