删除 java 中 LinkedList 中的节点

Question

I need to delete a Node from a linked list in java given an int that represents the index to be deleted. The head and tail of the list are defined outside of the method, they are defined in the class. I have defined the next node, and the data inside the node in another public class and have getters and setters for them. I need to return the data that was found in the node to be deleted and then adjust the head, tail and size (a variable defined in the class) accordingly.

public class myExample<T> {
    private Node<T> head;
    private Node<T> tail;
    private int size;

    public T removeAtIndex(int index) {
        if (index < 1 | (index + 1) > size) {
            throw new IllegalArgumentException("Index out of bounds");
        }
        Node tempNode = head;
        if (index == 0) {
            head = tempNode.getNext();
        }
        for (int i = 0; tempNode != null && i < index - 1; i++) {
            tempNode.setNext(tempNode);
        }
        return (T) tempNode.getNext().getNext();
        tempNode.setNext(tempNode.getNext().getNext());
        tempNode.setNext(tempNode.getNext());
    }
}

Answer 1

Instead of providing a direct answer to that question, I shall suggest a general methodology to target those kinds of questions.

To target those questions, first of all, you need to design the algorithm. As I see, you already figured out to have a temporary variable and let it traverse the linkedlist. However, it does not seem to be mature enough yet.

Secondly, you need to think about data encapsulations and responsibilities of the classes. I see that your myexample class holds three fields: head , tail , and size . So, what is the responsibility of myexample ? Is that a linkedlist wrapper implementation? If so, it needs to have other appropriate methods. You need to decide the roles and responsibilities of the classes.

By the way, having a tail resembles that the implementation is a Doubly-linked-list . However, your code does not have anything regarding pre links. It seems you need to fix that also.

Then, after you have something sketched up, you can start coding. Your first task in that implementation phase is, convert your thoughts to compilable programming language statements. So, type your code, and when you are done, compile it. Your uploaded code does not compile. You need to fix that.

It is also a good idea to have a test case, so that you can run and debug your code. You need to think about and design the details of the test case. In your example, the test code, should create a linked list and call removeAtIndex .

Consider that piece of code:

    for (int i = 0; tempNode != null && i < index - 1; i++) {
        tempNode.setNext(tempNode);
    }

Let's trace that. Prior to the loop, tempNode is assigned to something (actually head ). The loop iterates, and the next pointer of tempNode is assigned to itself (thus losing the links to the rest of the linked list). You do not update tempNode in the loop, so the code does that index-1 number of times. The loop breaks the links in the first iteration, and then does nothing in the following iterations. It seems there is a bug in that loop, and I think you have noticed what the bug is, and how to fix it.