java与数据结构(3)---java实现循环链表

循环链表：将单链表中尾结点的指针由空指针改为指向头结点，就使整个单链表形成一个环，这种首尾相接的单链表称为单链表循环表，即循环链表。

循环链表与单链表最重要的区别是：尾结点的指针，不再是p->next = null;而是：p->next=head。

接口

 1 //接口类
 2 interface Listable<T> {
 3     
 4     public void clear();
 5 
 6     public boolean isEmpty();
 7 
 8     public int Length();
 9 
10     public T getElement(int index);
11 
12     public boolean add(T element);
13 
14     public boolean addHead(T element);
15 
16     public boolean addByIndex(int index, T element);
17 
18     public boolean add(Listable<T> list);
19 
20     public T remove(int index);
21 
22     public boolean removeAll();
23 
24     public T remove(T element);
25 
26     public T setElement(int index,T element);
27 
28 }

节点类

 1 //结点类
 2 class Node<T> {
 3     private T data;
 4     private Node next;
 5 
 6     Node(T data, Node next) {
 7         this.data = data;
 8         this.next = next;
 9     }
10 
11     Node(T data) {
12         this(data,null);
13     }
14 
15     Node() {
16         this(null,null);
17     }
18 
19     public T getData() {
20         return this.data;
21     }
22 
23     public Node getNext() {
24         return this.next;
25     }
26 
27     public void setData(T data) {
28         this.data = data;
29     }
30 
31     public void setNext(Node next) {
32         this.next = next;
33     }
34 
35     public String toString() {
36         return getData().toString();
37     }
38 
39 }

接口实现类

  1 class CircularLinkedList<T> implements Listable<T> {
  2     public Node<T> head,tail;
  3 
  4 //  建空表，头为结点和尾结点都指向自己
  5     CircularLinkedList() {
  6         this(null);
  7     }
  8 
  9 //  建表，如果参数为空，建空表；若参数不为空，建一张有头有尾的结点，尾结点的指针指向头结点
 10     CircularLinkedList(T data) {
 11         if(data == null) {
 12             head = new Node<T>(data,null);//创建头结点，数据为data,指针为空
 13             tail = head;//尾结点和头结点相同
 14             tail.setNext(head);//尾结点指针域指向头结点，使首尾形成环
 15         }else {
 16             head = new Node<T>();
 17             tail = new Node<T>(data,head);
 18             head.setNext(tail);//等价于head.next = tail;
 19         }
 20     }
 21     
 22 //  清空链表，头=尾，this = null;
 23     public void clear() {
 24         removeAll();
 25         head.setNext(tail);
 26         tail.setNext(head);
 27         head = tail;
 28     }
 29     
 30 //  如果头=尾，返回true;否则，返回false
 31     public boolean isEmpty() {
 32         return tail == head;
 33     }
 34 
 35 //  获取链表当前元素个数，即表长
 36     public int Length() {
 37         int len = 0;
 38         Node<T> temp = head;
 39         while(temp.getNext() != head) {
 40             len++;
 41             temp = temp.getNext();
 42         }
 43         return len;
 44     }
 45     
 46 //  取index处的数据元素
 47     public T getElement(int index) {
 48         if(index < 0) return null;
 49         Node<T> temp = head;
 50         int j = 0;
 51         while(j <= index && temp.getNext() != head) {
 52             j++;
 53             temp = temp.getNext();
 54         }
 55         return temp.getData();
 56     }
 57 
 58 //  将参数链表添加到当前链表的后面
 59     public boolean add(Listable<T> list) {
 60         CircularLinkedList<T> slist = (CircularLinkedList<T>)list;
 61         tail.setNext(slist.head.getNext());
 62         slist.tail.setNext(head);
 63         slist.head.setNext(null);
 64         slist.head = null;
 65         return true;
 66     }
 67 
 68 //  尾添
 69     public boolean add(T element) {
 70         if(element == null) return false;
 71         Node<T> temp = new Node<T>(element,head);
 72         tail.setNext(temp);
 73         tail = temp;
 74         return true;
 75     }
 76 
 77 //  首添
 78     public boolean addHead(T element) {
 79         if(element == null) return false;
 80         Node<T> temp = new Node<T>(element,head.getNext());
 81         head.setNext(temp);
 82         return true;
 83     }
 84 
 85 //  任意位置添加
 86     public boolean addByIndex(int index, T element) {
 87         if(element == null) return false;
 88         if(index <= 0) 
 89             addHead(element);
 90         if(index >= Length())
 91             add(element);
 92         if(index > 0 && index < Length()) {
 93             int j = 0;
 94             Node<T> temp = head;
 95             Node<T> tempNext = temp.getNext();
 96             while(j < index && tempNext != head) {
 97                 j++;
 98                 temp = tempNext;
 99                 tempNext = tempNext.getNext();
100             }
101             Node<T> node = new Node<T>(element,tempNext);
102             temp.setNext(node);
103         }
104         return true;
105     }
106 
107 //  删除循环表中所有的数据元素
108     public boolean removeAll() {
109         if(isEmpty()) return false;
110         Node<T> tempNext = head.getNext();
111         while(tempNext != head) {
112             tempNext = tempNext.getNext();
113             head.setNext(tempNext);
114         }
115         return true;
116     }
117     
118 //  删除指定位置上的元素
119     public T remove(int index) {
120         if(isEmpty()) return null;
121         T element = null;
122         if(index <= 0) 
123             return removeHead();
124         if(index > Length())
125             index = Length()-1;
126         if(index > 0) {
127             int j = 0;
128             Node<T> temp = head;
129             Node<T> tempNext = head.getNext();
130             while(j < index && tempNext != head) {
131                 temp = tempNext;
132                 tempNext = tempNext.getNext();
133                 j++;
134             }
135             element = tempNext.getData();
136             temp.setNext(tempNext.getNext());
137         }
138         return element;
139     }
140     
141 //  删除表中的第一条element的数据
142     public T remove(T element) {
143         if(isEmpty()) return null;
144         if(element == null) return null;
145         Node<T> temp = head.getNext();
146         while(temp != head) {
147             if(!(element.equals(temp.getData()))) {
148                 temp = temp.getNext();
149             }else{
150                 return element;
151             }
152         }
153         return null;
154     }
155 
156 //  删除表头数据
157     private T removeHead() {
158         if(isEmpty()) return null;
159         Node<T> firstNode = head.getNext();
160         T element = firstNode.getData();
161         head.setNext(head.getNext().getNext());
162         return element;
163     }
164     
165 //  修改指定位置上的数据元素，并将原数据返回给T
166     public T setElement(int index,T element) {
167         if(isEmpty()) return null;
168         if(element == null) return null;
169         T tempEle = null;
170         if(index < 0) {
171             return null;
172         }
173         if(index >= Length()-1) {
174             index = Length() - 1;
175             tempEle = tail.getData();
176             tail.setData(element);
177             return tempEle;
178         }else if(index > 0 && index < Length()-1) {
179             Node<T> temp = head;
180             int j = 0;
181             while(j < index && temp.getNext() != head) {
182                 j++;
183                 temp = temp.getNext();
184             }
185             tempEle = temp.getData();
186             temp.setData(element);
187         }
188         return tempEle;    
189     }
190     
191 //  重写父类toString()方法
192     public String toString() {
193         if(isEmpty())
194             return "[ ]";
195         StringBuffer sb = new StringBuffer();
196         sb.append("[ ");
197         int L = Length();
198         for(int i = 0; i < L; i++) {
199             sb.append(getElement(i)+" ");
200         }
201         sb.append("]");
202         return sb.toString();
203     }
204 }

测试类

 1 package list;
 2 
 3 /*
 4 *@author Nora-Xie 
 5 *@time 2013-10-04 PM1708
 6 *java实现循环链表
 7 */
 8 
 9 public class TestCircularLinkedList {
10     public static void main(String[] args) {
11         Listable<String> list = new CircularLinkedList<String>("a");
12         list.add("b");
13         list.add("c");
14         list.add("d");
15         list.add("f");
16         System.out.println(list);
17         list.setElement(4,"e");
18         list.add("f");
19         System.out.println(list);
20         System.out.println(list);
21         list.addByIndex(1,"B");
22         System.out.println(list.Length()+"list="+list);
23         list.addHead("A");
24         System.out.println(list.Length()+"list="+list);
25         list.remove(0);
26         System.out.println(list.Length()+"list="+list);
27         list.remove(9);
28         System.out.println(list.Length()+"list="+list);
29         Listable<String> list1 = new CircularLinkedList<String>( );
30         list1.add("1");
31         list1.add("2");
32         list1.add("3");
33         list1.add("4");
34         list1.add("5");
35         list1.add("6");
36         list1.add("7");
37         list1.add("8");
38         list.add(list1);
39         System.out.println(list);
40         list.clear();
41         System.out.println(list.isEmpty());
42         System.out.println(list.Length()+"list="+list);
43     }
44 }