一、链表
1.1 概述
链表是真正动态的数据结构，最简单的动态数据结构，基本用于辅助组成其他数据结构。
数据存储在“节点”（Node）中
优点：真正的动态，不需要处理固定容量的问题
缺点：丧失了随机访问的能力
1.2 链表使用的基本功能
定义Node节点
private class Node{
public E e;
public Node next;
public Node(E e, Node next){
this.e = e;
this.next = next;
}
public Node(E e){
this(e, null);
}
public Node(){
this(null,null);
}
@Override
public String toString() {
return e.toString();
}
}
向链表中添加元素
具体代码实现：
//向链表中间添加元素
//在链表的index(0-based)位置添加新的元素e
public void add(int index, E e){
if(index < 0 || index > size)
throw new IllegalArgumentException("Add failed.Illeagl failed.");
Node prev = dummyHead;
for (int i = 0; i < index; i++) {
prev = prev.next;
}
// Node node = new Node(e);
// node.next = prev.next;
// prev.next = node;
prev.next = new Node(e, prev.next);
size++;
}
向链表中删除元素
具体代码实现：
//链表中删除index(0-based)位置的元素，返回删除的元素
public E remove(int index){
if(index < 0 || index >= size)
throw new IllegalArgumentException("Remove failed.Illeagl failed.");
Node pre = dummyHead;
for (int i = 0; i < index; i++) {
pre = pre.next;
}
Node retNode = pre.next;
pre.next = retNode.next;
retNode.next = null;
size--;
return retNode.e;
}
链表功能的实现及测试类
public class LinkedList<E> {
private class Node{
public E e;
public Node next;
public Node(E e, Node next){
this.e = e;
this.next = next;
}
public Node(E e){
this(e, null);
}
public Node(){
this(null,null);
}
@Override
public String toString() {
return e.toString();
}
}
private Node dummyHead;
private int size;
public LinkedList(){
dummyHead = new Node(null, null);
size = 0;
}
//获取链表中的元素个数
public int getSize(){
return size;
}
//返回链表是否为空
public boolean isEmpty(){
return size == 0;
}
//向链表头添加元素
public void addFirst(E e){
// Node node = new Node(e);
// node.next = head;
// head = node;
add(0, e);
}
//向链表中间添加元素
//在链表的index(0-based)位置添加新的元素e
public void add(int index, E e){
if(index < 0 || index > size)
throw new IllegalArgumentException("Add failed.Illeagl failed.");
Node prev = dummyHead;
for (int i = 0; i < index; i++) {
prev = prev.next;
}
// Node node = new Node(e);
// node.next = prev.next;
// prev.next = node;
prev.next = new Node(e, prev.next);
size++;
}
//在链表的末尾添加新的元素e
public void addLast(E e){
add(size, e);
}
//获得链表的第index(0-based)个位置的元素
//在链表中不是一个常用的操作
public E get(int index){
if(index < 0 || index > size)
throw new IllegalArgumentException("Add failed.Illeagl failed.");
Node cur = dummyHead.next;
for (int i = 0; i < index; i++) {
cur = cur.next;
}
return cur.e;
}
//获得链表的第一个元素
public E getFirst(){
return get(0);
}
//获得链表的最后一个元素
public E getLast(){
return get(size - 1);
}
//修改链表的第index(0-based)个位置的元素
//在链表中不是一个常用的操作
public void set(int index, E e){
if(index < 0 || index > size)
throw new IllegalArgumentException("Add failed.Illeagl failed.");
Node cur = dummyHead.next;
for (int i = 0; i < index; i++) {
cur = cur.next;
}
cur.e = e;
}
//查找链表中是否有元素e
public boolean contains(E e){
Node cur = dummyHead.next;
while(cur != null){
if(cur.e.equals(e)){
return true;
}
cur = cur.next;
}
return false;
}
//链表中删除index(0-based)位置的元素，返回删除的元素
public E remove(int index){
if(index < 0 || index >= size)
throw new IllegalArgumentException("Remove failed.Illeagl failed.");
Node pre = dummyHead;
for (int i = 0; i < index; i++) {
pre = pre.next;
}
Node retNode = pre.next;
pre.next = retNode.next;
retNode.next = null;
size--;
return retNode.e;
}
//从链表中删除第一个元素
public E removeFirst(){
return remove(0);
}
//从链表中删除最后一个元素
public E removeLast(){
return remove(size - 1);
}
@Override
public String toString() {
StringBuilder res = new StringBuilder();
// Node cur = dummyHead.next;
// while (cur != null){
// res.append(cur + "->");
// cur = cur.next;
// }
for (Node cur = dummyHead.next; cur != null; cur = cur.next){
res.append(cur + "->");
}
res.append("null");
return res.toString();
}
public static void main(String[] args) {
LinkedList<Integer> linkedList = new LinkedList<>();
for (int i = 0; i < 5; i++) {
linkedList.addFirst(i);
System.out.println(linkedList);
}
linkedList.add(2, 666);
System.out.println(linkedList);
linkedList.remove(2);
System.out.println(linkedList);
linkedList.removeFirst();
System.out.println(linkedList);
linkedList.removeLast();
System.out.println(linkedList);
}
}
二、链表实现栈操作
使用第二章中的栈接口，创建第一节中的链表实现对象，实现栈的操作，具体如下：
public class LinkedListStack<E> implements Stack<E> {
private LinkedList<E> list;
public LinkedListStack(){
list = new LinkedList<>();
}
@Override
public int getSize() {
return list.getSize();
}
@Override
public boolean isEmpty() {
return list.isEmpty();
}
@Override
public void push(E value) {
list.addFirst(value);
}
@Override
public E pop() {
return list.removeFirst();
}
@Override
public E peek() {
return list.getFirst();
}
@Override
public String toString() {
StringBuilder res = new StringBuilder();
res.append("Stack : top");
res.append(list);
return res.toString();
}
public static void main(String[] args) {
LinkedListStack<Integer> stack = new LinkedListStack<>();
for (int i = 0; i < 5; i++) {
stack.push(i);
System.out.println(stack);
}
stack.pop();
System.out.println(stack);
}
}
三、链表实现队列操作
使用第二章中的队列接口，创建无头节点的链表实现队列操作，具体如下：
public class LinkedListQueue<E> implements Queue<E> {
private class Node{
public E e;
public LinkedListQueue.Node next;
public Node(E e, LinkedListQueue.Node next){
this.e = e;
this.next = next;
}
public Node(E e){
this(e, null);
}
public Node(){
this(null,null);
}
@Override
public String toString() {
return e.toString();
}
}
private Node head,tail;
private int size;
public LinkedListQueue(){
head = null;
tail = null;
size = 0;
}
@Override
public int getSize() {
return size;
}
@Override
public boolean isEmpty() {
return size == 0;
}
@Override
public void enqueue(E e) {
if(tail == null){
tail = new Node(e);
head = tail;
}else{
tail.next = new Node(e);
tail = tail.next;
}
size++;
}
@Override
public E dequeue() {
if (isEmpty())
throw new IllegalArgumentException("Cannot dequeue form any empty queue.");
Node retNode = head;
head = head.next;
retNode.next = null;
if (head == null)
tail = null;
return retNode.e;
}
@Override
public E getFront() {
if (isEmpty())
throw new IllegalArgumentException("Cannot getFront form any empty queue.");
return head.e;
}
@Override
public String toString() {
StringBuilder res = new StringBuilder();
res.append("Queue : front ");
Node cur = head;
while (cur != null){
res.append(cur + "->");
cur = cur.next;
}
res.append("Null tail");
return res.toString();
}
public static void main(String[] args) {
LinkedListQueue<Integer> queue = new LinkedListQueue<>();
for (int i = 0; i < 10; i++) {
queue.enqueue(i);
System.out.println(queue);
if(i % 3 == 2){
queue.dequeue();
System.out.println(queue);
}
}
}
}
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