《Java数据结构与算法》笔记-CH5-链表-2单链表，增加根据关键字查找和删除

 /**
  * Link节点 有数据项和next指向下一个Link引用
  */
 class Link {
     private int iData;// 数据
     private double dData;// 数据
     public Link next;// 下一个link节点的引用

     public int getiData() {
         return iData;
     }

     public Link(int i, double d) {
         iData = i;
         dData = d;
     }

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

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

 /**
  * 链表类 维护一个头节点
  */
 class LinkList {
     private Link first;

     /**
      * 初始化的时候头结点置空
      */
     public LinkList() {
         first = null;
     }

     /**
      * 头结点是空代表链表为空
      *
      * @return
      */
     public boolean isEmpty() {
         return first == null;
     }

     /**
      * 向链表头插入Link节点
      *
      * @param link
      */
     public void insertFirst(Link link) {
         link.next = first;// 要插入的节点的next指针指向链表的头节点
         first = link;// 链表的头结点指向被插入的节点
     }

     /**
      * 从链表头删除头结点并返回
      *
      * @return
      */
     public Link deleteFirst() {
         Link temp = first;// temp临时存上头结点
         first = first.next;// 将头节点的next指针指向下一个节点
         return temp;// 返回temp
     }

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

     /**
      * 根据key寻找节点
      *
      * @param key
      * @return
      */
     public Link find(int key) {
         Link curr = first;
         while (curr.getiData() != key) {
             if (curr.next == null)
                 return null;
             else
                 curr = curr.next;
         }
         return curr;
     }

     /**
      * 根据key值删除节点
      *
      * @param key
      * @return
      */
     public Link deleteByKey(int key) {
         Link current = first;
         Link previous = first;
         // 根据key值遍历
         while (current.getiData() != key) {
             if (current.next == null)//找不到，返回null
                 return null;
             else {
                 previous = current;
                 current = current.next;
             }
         }
         //找到，此时头结点就是要删除的节点，直接把头结点置为头结点的next节点
         if (current == first)
             first = first.next;
         else//找到，此时把前一个节点的next指向当前节点的next即可
             previous.next = current.next;
         return current;
     }

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

 public class LinkListDemo {
     public static void main(String[] args) {
         LinkList ll = new LinkList();
         for (int i = 0; i < 10; i++) {
             Link l = new Link(i, i + 11.23);
             ll.insertFirst(l);
             ll.displayList();
         }
         ll.deleteFirst();
         ll.deleteFirst();
         ll.displayList();
         Link l3 = ll.find(3);
         System.out.println("key 为3的节点是: "+l3.toString());
         ll.deleteByKey(3);
         System.out.print("删除该节点后，链表是：");
         ll.displayList();
     }
 }