Question

我觉得我过于复杂化，因为我发现有太多的边界情况。这是大学的作业，所以请只给我提示，而不是我可以复制/粘贴的代码。我正在尝试创建一个优先级队列来命令包含字符的元素。应根据优先级值排列它们，如果优先级存在冲突，则按字母顺序排列。我遇到的问题是插入元素。这是我目前的代码：

public void insertItem(int priority, char content) {
        boolean isSpecialCase = false;
        PList current;

        if (isEmpty()) {
            high = new PList(priority, content, null, null);
            low=high;
            System.out.println(content + " has been added to an empty list");
            isSpecialCase = true;

        }

        if (priority >= high.getPriority() && content >= high.getContent() && !isSpecialCase) {
            PList newItem = new PList(priority, content, high, null);
            high.setBehind(newItem);
            high = newItem;
            isSpecialCase = true;
            System.out.println(content + " has been added to a non empty list - highest priority");
        }
       if (priority < low.getPriority() && !isSpecialCase) {
            PList newItem = new PList(priority, content, null, low);
            low.setNext(newItem);
            low = newItem;
            isSpecialCase = true;
            System.out.println(content + " has been added to a non empty list - absolute lowest priority");
        }
        if (priority == low.getPriority() && content > low.getContent() && !isSpecialCase) {
            PList newItem = new PList(priority, content, low, low.getBehind());
            low.getBehind().setNext(newItem);
            low.setBehind(newItem);

            isSpecialCase = true;
            System.out.println(content + " has been added to a non empty list - lowest priority-highest char");

        }
        if (priority == low.getPriority() && !isSpecialCase) {
            if (content < low.getContent()) {
                PList newItem = new PList(priority, content, null, low);
                low.setNext(newItem);
                low = newItem;
                isSpecialCase = true;
                System.out.println(content + " has been added to a non empty list -lowest priority");
            }
        }



        current = high;
        while (current.getNext() != null && !isSpecialCase) {
            if (current.getPriority() >= priority) {
                if (current.getContent() > content) {
                    PList newItem = new PList(priority, content, current.getNext(), current);
                    current.getNext().setBehind(newItem);
                    current.setNext(newItem);
                    break;
                }
            }
            current = current.getNext();
        }
    }

这看起来很混乱，有些重复，所以这就是为什么我认为我走错了路。它适用于大多数情况，但例如我运行时得到一个nullPointer：

  PriQueue p = new PriQueue();
    p.insertItem(5, 'a');
    p.insertItem(5, 'a');
    p.insertItem(4, 'x');
    p.insertItem(4, 'a');
    p.insertItem(4, 'x');

还有一些情况，它不会在没有任何错误的情况下将所有元素放入队列中。

提前谢谢

Answer 1

我同意你过度复杂化，但没有给出完整的解释，你应该考虑在你的Comparable项目上实施PList界面。然后，当您插入新项目时，您可以遍历列表，直到listNode.compareTo(newNode) > 0，这就是您插入的位置。

如何创建一个同时考虑元素内容的优先级队列？

1 个答案: