Java 模拟双端链表，以链表实现栈和队列

双端链表：

双端链表与传统链表非常相似.只是新增了一个属性-即对最后一个链结点的引用rear

这样在链尾插入会变得非常容易，只需改变rear的next为新增的结点即可，而不需要循环搜索到最后一个节点

所以有insertFirst、insertLast

删除链头时，只需要改变引用指向即可；删除链尾时，需要将倒数第二个结点的next置空，

而没有一个引用是指向它的，所以还是需要循环来读取操作

/** * 双端链表 * @author stone */public class TwoEndpointList<T> {private Link<T> head;//首结点private Link<T> rear;//尾部指针public TwoEndpointList() {}public T peekHead() {if (head != null) {return head.data;}return null;}public boolean isEmpty() {return head == null;}public void insertFirst(T data) {// 插入 到 链头Link<T> newLink = new Link<T>(data);newLink.next = head; //新结点的next指向上一结点head = newLink;}public void insertLast(T data) {//在链尾 插入Link<T> newLink = new Link<T>(data);if (head == null) {rear = null;}if (rear != null) {rear.next = newLink;} else {head = newLink;head.next = rear;}rear = newLink; //下次插入时，从rear处插入}public T  deleteHead() {//删除 链头if (isEmpty()) return null;Link<T> temp = head;head = head.next; //变更首结点，为下一结点if (head == null) {<span style="white-space:pre"></span>rear = head;}return temp.data;}public T find(T t) {if (isEmpty()) {return null;}Link<T> find = head;while (find != null) {if (!find.data.equals(t)) {find = find.next;} else {break;}}if (find == null) {return null;}return find.data; }public T delete(T t) {if (isEmpty()) {return null;} else {if (head.data.equals(t)) {Link<T> temp = head;head = head.next; //变更首结点，为下一结点return temp.data;}}Link<T> p = head;Link<T> q = head;while (!p.data.equals(t)) {if (p.next == null) {//表示到链尾还没找到return null;} else {q = p;p = p.next;}}q.next = p.next;return p.data;}public void displayList() {//遍历System.out.println("List (head-->last):");Link<T> current = head;while (current != null) {current.displayLink();current = current.next;}}public void displayListReverse() {//反序遍历if (isEmpty()) {return;}Link<T> p = head, q = head.next, t;while (q != null) {//指针反向，遍历的数据顺序向后t = q.next; //no3if (p == head) {// 当为原来的头时，头的.next应该置空p.next = null;}q.next = p;// no3 -> no1  pointer reversep = q; //start is reverseq = t; //no3 start}//上面循环中的if里，把head.next 置空了, 而当q为null不执行循环时，p就为原来的最且一个数据项，反转后把p赋给headhead = p; displayList();}class Link<T> {//链结点T data;//数据域Link<T> next; //后继指针，结点链域Link(T data) {this.data = data;}void displayLink() {System.out.println("the data is " + data.toString());}}public static void main(String[] args) {TwoEndpointList<Integer> list = new TwoEndpointList<Integer>();list.insertLast(1);list.insertFirst(2);list.insertLast(3);list.insertFirst(4);list.insertLast(5);list.displayList();list.deleteHead();list.displayList();System.out.println("find:" + list.find(6));System.out.println("find:" + list.find(3));System.out.println("delete find:" + list.delete(6));System.out.println("delete find:" + list.delete(5));list.displayList();System.out.println("----reverse----");list.displayListReverse();}}

打印

List (head-->last):the data is 4the data is 2the data is 1the data is 3the data is 5List (head-->last):the data is 2the data is 1the data is 3the data is 5find:nullfind:3delete find:nulldelete find:5List (head-->last):the data is 2the data is 1the data is 3----reverse----List (head-->last):the data is 3the data is 1the data is 2

/** * 使用链表实现栈  ，用前插 单链表就能实现， * 本类采用双端链表实现 * @author stone * */public class LinkStack<T> {private TwoEndpointList<T> datas;public LinkStack() {datas = new TwoEndpointList<T>();}// 入栈public void push(T data) {datas.insertFirst(data);}// 出栈public T pop() {return datas.deleteHead();}// 查看栈顶public T peek() {return datas.peekHead();}//栈是否为空public boolean isEmpty() {return datas.isEmpty();}public static void main(String[] args) {LinkStack<Integer> stack = new LinkStack<Integer>();for (int i = 0; i < 5; i++) {stack.push(i);}for (int i = 0; i < 5; i++) {Integer peek = stack.peek();System.out.println("peek:" + peek);}for (int i = 0; i < 6; i++) {Integer pop = stack.pop();System.out.println("pop:" + pop);}System.out.println("----");for (int i = 5; i > 0; i--) {stack.push(i);}for (int i = 5; i > 0; i--) {Integer peek = stack.peek();System.out.println("peek:" + peek);}for (int i = 5; i > 0; i--) {Integer pop = stack.pop();System.out.println("pop:" + pop);}}}

打印

peek:4peek:4peek:4peek:4peek:4pop:4pop:3pop:2pop:1pop:0pop:null----peek:1peek:1peek:1peek:1peek:1pop:1pop:2pop:3pop:4pop:5

/** * 链表实现 队列  用双端链表实现 * @author stone * */public class LinkQueue<T> {private TwoEndpointList<T> list;public LinkQueue() {list = new TwoEndpointList<T>();}//插入队尾public void insert(T data) {list.insertLast(data);}//移除队头public T remove() {return list.deleteHead();}//查看队头public T peek() {return list.peekHead();}public boolean isEmpty() {return list.isEmpty();}public static void main(String[] args) {LinkQueue<Integer> queue = new LinkQueue<Integer>();for (int i = 1; i < 5; i++) {queue.insert(i);}for (int i = 1; i < 5; i++) {Integer peek = queue.peek();System.out.println("peek:" + peek);}for (int i = 1; i < 5; i++) {Integer remove = queue.remove();System.out.println("remove:" + remove);}System.out.println("----");for (int i = 5; i > 0; i--) {queue.insert(i);}for (int i = 5; i > 0; i--) {Integer peek = queue.peek();System.out.println("peek2:" + peek);}for (int i = 5; i > 0; i--) {Integer remove = queue.remove();System.out.println("remove:" + remove);}}}

打印

peek:1peek:1peek:1peek:1remove:1remove:2remove:3remove:4----peek2:5peek2:5peek2:5peek2:5peek2:5remove:5remove:4remove:3remove:2remove:1