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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