《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();
    }
}