如何在确保最后一个元素指向第一个元素的同时将其排入圆形链表？

Question

I'm trying to build an enqueue method for a circular linked list. Here is what I am have so far:

public class Test<T> implements UnboundedQueueInterface<T> {
    protected LLNode<T> rear;
    protected LLNode<T> current;

    public Test() {
        rear = null;
        current = null;
    }

    @Override
    public boolean isEmpty() {
        if (rear == null) {
            return true;
        } else {
            return false;
        }
    }

    @Override
    public void enqueue(T element) {
        LLNode<T> node = new LLNode<T>(element);

        if (rear == null) {
            rear = node;
            node.setLink(rear);
        } else {
            LLNode<T> temp = rear;
            rear = node;
            node.setLink(temp);
        }
    }
}

Instead of the last element linking to the first, it links to the second to last and so forth. Any ideas?

Answer 1

LLNode<T> temp = rear;
rear = node;
node.setLink(temp);

temp holds the original rear. When you call setLink, you are saying to point to temp, which is the original rear. Instead, you need to point to rear.getLink() to point to the first element (since the old rear was pointing to the first element).

After that, you still have another link to fix. temp (the old rear) is still pointing to the first element, but it should be updated.