Question

我正在研究链接列表。在Cracking the Coding Interview一书的帮助下，我创建了以下代码来创建链接列表，在其末尾添加元素并打印元素。但是，当我运行代码时，它只返回＆＃34; null＆＃34;而不是打印列表，即＆＃34; Sanchez＆＃34;。＆＃34;厄齐尔＆＃34;和＃34; Welbeck＆＃34;。帮助

public class CreateLinkedList{

    static class Node{
        String PlayerName;
        Node next = null;

        //Constructor
        Node(String PName){
            PlayerName = PName;
        }

        //Method to insert a Node
        void InsertNodeAtEnd(String PlayerName){
            Node transition = new Node(PlayerName);
            Node n = this;
            while(n.next != null){
                n = n.next;
                }
            n.next = transition;            
            }       

        //Method to print all elements of linked list
        void PrintList(){
            Node n = this;
            while (n.next != null){
                System.out.println(n.PlayerName + "\n");
                n = n.next;
            }
        }
    }

    public static void main(String[] args) {

        Node first = new Node("Sanchez");
        first.InsertNodeAtEnd("Ozil");
        first.InsertNodeAtEnd("Welbeck");
        first.PrintList();
    }   
}

Answer 1

public class CreateLinkedList {
static class Node {
    String PlayerName;
    Node next = null;

    // Constructor
    Node(String PName) {
        PlayerName = PName;
    }

    // Method to insert a Node
    void InsertNodeAtEnd(String PlayerName) {
        Node transition = new Node(PlayerName);
        Node n = this;
        while (n.next != null) {
            n = n.next;
        }
        n.next = transition;
    }

    // Method to print all elements of linked list
    void PrintList() {
        Node n = this;
        while (n != null) {
            System.out.println(n.PlayerName + "\n");
            n = n.next;
        }
    }
}

public static void main(String[] args) {

    Node first = new Node("Sanchez");
    first.InsertNodeAtEnd("Ozil");
    first.InsertNodeAtEnd("Welbeck");
    first.PrintList();
}
}

输出

Sanchez

Ozil

Welbeck

Answer 2

在PrintList中，迭代每个元素，最后一次迭代丢失，所以我改变了循环条件

void PrintList(){
                Node n = this;
                while (n != null){
                    System.out.println(n.PlayerName + "\n");
                    n = n.next;
                }
            }

Answer 3

我很确定问题出在你添加到链表时。

Node n = this;

这指向了班级本身，这不是一个节点您应该在表示第一个Node的类中实现Node变量。所以像这样：

public class CreateLinkedList{


static class Node{
    //all this stuff seemed fine
    }

Node first = null;//represents first item

    //Method to insert a Node
    void InsertNodeAtEnd(String PlayerName){
        Node transition = new Node(PlayerName);
        Node n = first;
       if(n!=null){
            while(n.next != null){
               n = n.next;
               }
           n.next = transition;            
        }
       else
         first = transition;



    //Method to print all elements of linked list
    void PrintList(){
        Node n = first;
        while (n.next != null){
            System.out.println(n.PlayerName + "\n");
            n = n.next;
        }
    }
}

public static void main(String[] args) {

    Node first = new Node("Sanchez");
    first.InsertNodeAtEnd("Ozil");
    first.InsertNodeAtEnd("Welbeck");
    first.PrintList();
}   
}'

Answer 4

在printList中迭代时使用以下作为检查条件：

N！= NULL

而不是

n.next！= null

在您的代码中，当您比较下一个节点而不是当前节点时，循环正在跳过最后一次迭代。

正确的方法是：

//Method to print all elements of linked list
 void PrintList(){
    Node n = this;
    while (n != null){
        System.out.println(n.PlayerName + "\n");
        n = n.next;
    }
}

Java - 遍历链表仅返回null

4 个答案: