2019-05-22：请用 Java 实现一个简单的单链表？ #59
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定义链表：
public class ListNode {
int val;
ListNode next;
public ListNode(int val){
this.val = val;
}
}
基本操作：
public class SingleLinkedList {
/**链表的头结点*/
ListNode head = null;
/**
* 链表添加结点:
* 找到链表的末尾结点，把新添加的数据作为末尾结点的后续结点
* @param data
*/
public void addNode(int data){
ListNode newNode = new ListNode(data);
if(head == null){
head = newNode;
return;
}
ListNode temp = head;
while(temp.next != null){
temp = temp.next;
}
temp.next = newNode;
}
/**
* 链表删除结点:
* 把要删除结点的前结点指向要删除结点的后结点，即直接跳过待删除结点
* @param index
* @return
*/
public boolean deleteNode(int index){
if(index<1 || index>length()){//待删除结点不存在
return false;
}
if(index == 1){//删除头结点
head = head.next;
return true;
}
ListNode preNode = head;
ListNode curNode = preNode.next;
int i = 1;
while(curNode != null){
if(i==index){//寻找到待删除结点
preNode.next = curNode.next;//待删除结点的前结点指向待删除结点的后结点
return true;
}
//当先结点和前结点同时向后移
preNode = preNode.next;
curNode = curNode.next;
i++;
}
return true;
}
/**
* 求链表的长度
* @return
*/
public int length(){
int length = 0;
ListNode curNode = head;
while(curNode != null){
length++;
curNode = curNode.next;
}
return length;
}
/**
* 打印结点
*/
public void printLink(){
ListNode curNode = head;
while(curNode !=null){
System.out.print(curNode.val+" ");
curNode = curNode.next;
}
System.out.println();
}
/**
* 查找正数第k个元素
*/
public ListNode findNode(int k){
if(k<1 || k>length()){//不合法的k
return null;
}
ListNode temp = head;
for(int i = 0; i<k-1; i++){
temp = temp.next;
}
return temp;
}
public static void main(String[]args){
SingleLinkedList myLinkedList = new SingleLinkedList();
//添加链表结点
myLinkedList.addNode(9);
myLinkedList.addNode(8);
myLinkedList.addNode(6);
myLinkedList.addNode(3);
myLinkedList.addNode(5);
//打印链表
myLinkedList.printLink();
System.out.println("链表结点个数为：" + myLinkedList.length());
myLinkedList.deleteNode(3);
myLinkedList.printLink();
}
} |
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收获了 |
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学习 |
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正好最近在看LinkedList的源码 可参考 LinkedList源码分析 |
单链表的结点类：public class Node {
// 当前节点的下一个结点变量
public Node next;
// 存放的数据
public int data;
// 构造器
public Node(int data) {
this.data = data;
}
}单链表的简单实现：/**
* 我是一只贪吃蛇
*/
public class SimpleLinkedList {
private Node head;
private static final int HEAD_NODE_DATA = -1;
public SimpleLinkedList() {
head = new Node(HEAD_NODE_DATA);
}
/**
* 获取当前单链表的长度
* @return 链表的长度
*/
public int length() {
Node temp = head;
if (temp == null) {
return 0;
}
int size = 1;
while (temp.next != null) {
temp = temp.next;
size = size + 1;
}
return size;
}
/**
* 直接在链表内插入一个结点
* 插入位置：链表最后面
* @param node 插入的结点
*/
public void addNode(Node node) {
Node currentNode = head;
if (currentNode == null) {
throw new IllegalArgumentException("the SimpleLinkedList is null, it should have nodes at least one.");
}
// 遍历单链表，找到当前链表的最后一个结点
while (currentNode.next != null) {
currentNode = currentNode.next;
}
// 将目标结点插入到末位结点的后面
currentNode.next = node;
}
/**
* 通过已知数据在链表内插入一个结点
* 插入位置：链表最后面
* @param data 结点中存储的数据
*/
public void addNode(int data) {
Node node = new Node(data);
Node currentNode = head;
if (currentNode == null) {
throw new IllegalArgumentException("the SimpleLinkedList is null, it should have nodes at least one.");
}
while (currentNode.next != null) {
currentNode = currentNode.next;
}
currentNode.next = node;
//System.out.print(node.data);
}
/**
* 在链表的指定位置插入一个结点
* @param index 插入位置
* @param data 结点数据
*/
public void addNode(int index, int data) {
Node node = new Node(data);
// 如果链表不为空，至少需要有一个结点
if (index < 1 || index > length() + 1) {
throw new IllegalArgumentException("the node position inserted is invalid, please check it up again.");
}
// 从第1个位置开始(head位置为0)
int count = 1;
Node currentNode = head;
while (currentNode.next != null) {
if (index == count++) {
// 找到插入点
// 现将当前插入点的node的后续链排到目标node之后
node.next = currentNode.next;
// 再将目标node插入到当前node的后面
currentNode.next = node;
System.out.print(node.data);
return;
}
currentNode = currentNode.next;
}
// 当前插入的位置是链表的末尾
if (index == length()) {
addNode(node);
}
}
/**
* 移除指定位置的结点
* @param index 位置
*/
public void removeNode(int index) {
// 不能少于一个结点，并且不能超过总长度
if (index < 1 || index > length() -1 ) {
throw new IllegalArgumentException("the node position removed is invalid, please check it up again.");
}
int count = 1;
Node current = head;
while (current.next != null) {
// 找到删除位置
if (index == count++) {
current.next = current.next.next;
return;
}
current = current.next;
}
}
/**
* 获取某个位置的结点
* @param location 目标结点的位置
* @return 目标结点
*/
public Node get(int location) {
Node node = null;
if (location < 1 || location > length() -1 ) {
throw new IllegalArgumentException("the node position queried is invalid, please check it up again.");
}
int count = 1;
Node current = head;
while (current.next != null) {
// 找到目标位置
if (location == count++) {
node = current.next;
}
current = current.next;
}
return node;
}
/**
* 打印链表内所有数据
* @return 链表数据
*/
public String toString() {
Node temp = head.next;
StringBuilder message = new StringBuilder();
while (temp != null) {
message.append(temp.data).append("\t");
temp = temp.next;
}
return message.toString();
}
}简单测试：public class Main {
public static void main(String[] args) {
SimpleLinkedList list = new SimpleLinkedList();
list.addNode(1);
list.addNode(2);
list.addNode(3);
list.addNode(4, 8);
System.out.println(list.toString());
list.removeNode(2);
System.out.println(list.toString());
System.out.println(list.get(3).data);
}
}最终运行结果： |
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上面两份代码，参数都是1开始算吗？如果是，那应该是if (location < 1 || location > length())，但一般是下标是从0开始吧，if (location < 0 || location > length() - 1) |
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结点类代码如下：
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