《Java数据结构与算法》笔记-CH5-链表-3双端链表

 /**
  * 双端链表的实现
  */
 class LinkA {
     public long dData;
     public LinkA next;

     public LinkA(long d) {
         dData = d;
     }

     public String toString() {
         return "[" + dData + "]";
     }

     public void displayLink() {
         System.out.println(toString());
     }
 }

 class FirstLastList {
     private LinkA first;// 头部
     private LinkA last;// 尾部

     public FirstLastList() {
         first = null;
         last = null;
     }

     public boolean isEmpty() {
         return first == null;
     }

     /**
      * 在头部插入节点
      */
     public void insertFirst(LinkA l) {
         if (isEmpty())
             last = l;
         l.next = first;
         first = l;
     }

     /**
      * 在尾部插入节点
      *
      * @param l
      */
     public void insertLast(LinkA l) {
         if (isEmpty())
             first = l;
         else
             last.next = l;
         last = l;
     }

     /**
      * 从头部删除一个节点
      *
      * @return
      */
     public long deleteFirst() {
         long temp = first.dData;
         if (first.next == null)
             last = null;
         first = first.next;
         return temp;
     }

     public String toString() {
         if (isEmpty())
             return "{}";
         LinkA current = first;
         StringBuilder sb = new StringBuilder();
         sb.append("{");
         while (current != null) {
             sb.append(current.toString()).append(",");
             if (current.next == null)
                 break;
             else
                 current = current.next;
         }
         sb.deleteCharAt(sb.length() - 1);
         sb.append("}");
         return sb.toString();
     }

     public void displayList() {
         System.out.println(toString());
     }
 }

 public class FirstLastListDemo {
     public static void main(String[] args) {
         FirstLastList fll = new FirstLastList();
         for (int i = 1; i < 10; i++) {
             System.out.println("插入:"+i);
             if (i % 2 == 0)//i为偶数调用insertFirst
                 fll.insertFirst(new LinkA(i));
             else//i为基数调用insertLast
                 fll.insertLast(new LinkA(i));
             fll.displayList();
         }
         System.out.println("插入完毕开始从头部删除");
         while(!fll.isEmpty()){
             fll.deleteFirst();
             fll.displayList();
         }
     }
 }