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 (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 && head.next == null) {
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; //no3
if (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 reverse
p = q; //start is reverse
q = 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head
head = 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 4 the data is 2 the data is 1 the data is 3 the data is 5 List (head-->last): the data is 2 the data is 1 the data is 3 the data is 5 find:null find:3 delete find:null delete find:5 List (head-->last): the data is 2 the data is 1 the data is 3 ----reverse---- List (head-->last): the data is 3 the data is 1 the data is 2
/**
* 使用链表实现栈
* @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:4 peek:4 peek:4 peek:4 peek:4 pop:4 pop:3 pop:2 pop:1 pop:0 pop:null ---- peek:1 peek:1 peek:1 peek:1 peek:1 pop:1 pop:2 pop:3 pop:4 pop:5
原文地址：http://blog.csdn.net/jjwwmlp456/article/details/40427949
