在链表中的特定节点之后插入

Question

这是我实现单向链表的完整 Java 源代码。我看过很多教程，他们一直在谈论在开始时插入一个节点。因此，我决定在我的代码中添加一个方法 insertAfterNode(int y)，我可以在其中在特定节点之后的节点内添加数据。

/*
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 * and open the template in the editor.
 */
package datastructures;

/**
 *
 * @author Administrator
 */
public class Link {

    int data;

    Link next;

    public Link(int d) {

        this.data = d;
    }

    public void display() {

        System.out.println(data);
    }


    public static class LinkedList {

        Link first;

        public void insertItemFirst(int x){

            Link newLink = new Link(x);

            newLink.next = first;
            first = newLink;


        }



        public Link deleteFirst() {

            Link temp = first;
            first = first.next;
            return temp;
        }

        public void displayList() {

            Link current = first;

            while (current != null) {

                current.display();
                current = current.next;

            }

        }

        // START Of METHOD


        public void insertAfterNode(int y) {

            // Considering LinkedList is Sorted
            Link newNode = new Link(y);

            Link current = first;

            while (current != null) {

                while (current.data < y) {

                    current = current.next;
                    newNode.next = current;
                    current = newNode;

                }

            }

        }





        //END Of METHOD

    }



    public static void main(String[] args) {

        LinkedList addelements = new LinkedList();

        addelements.insertItemFirst(20);
        addelements.insertItemFirst(30);
        addelements.insertItemFirst(40);
        addelements.insertItemFirst(50);
       addelements.insertAfterNode(44);



        addelements.displayList();

        System.out.println("After Calling Deletion Method Once ");

        addelements.deleteFirst();



        addelements.displayList();

    }

}

上面的代码在 Netbeans 中保持运行，我不得不停止构建以退出它。我相信我的方法实现有问题。请让我知道我的以下方法有什么问题：

 public void insertAfterNode(int y) {

            // Considering LinkedList is Sorted
            Link newNode = new Link(y);

            Link current = first;

            while (current != null) {

                while (current.data < y) {

                    current = current.next;
                    newNode.next = current;
                    current = newNode;

                }

            }

        }

没有上述方法，代码运行正常。

Answer 1

仅当 y 值大于 current.data 时，current Link 引用才会更改。例如，如果 fist.data 是 10，而 y 是 5，您的代码将永远不会终止。

您必须修改您的 while(current != null) 周期。不要使用内部 while.

Link newNode = new Link(y);
// "first" requires a special treatment, as we need to replace the "first" value
if(first.data > y){
    // insert the new Link as first element
    newNode.next = first;
    first = newNode;
} else {
    // we need the previous Link, because previous.next will be set to the newNode
    Link previous = first;
    Link current = first.next;

    while (current != null) {
        if(current.data < y) {
            previous = current;
            current = current.next;
        } else {
            // we insert newNode between previous and current
            // btw. what should happen if current.data == y?
            previous.next = newNode;
            newNode.next = current;
            break; // we are done, quit the cycle
        }
    }
    // if the newNode.next is null at this point, means we have not inserted it yet.
    // insert it as the last element in the list. previous is pointing at it.
    if(newNode.next == null){
        previous.next = newNode;
    }
} // end of else

P.S。我希望它有效，我还没有测试代码:)

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