仅具有2个参数的递归二进制搜索方法 [英] Recursive binary search method having only 2 arguments

问题描述

好的，这是给学校做的作业.我进行递归二进制搜索没有问题，但是赋值明确表示该方法应仅包含2个参数，列表和要搜索的项目.这是我有点迷路的地方.

Okay so this is for a school assignment. I have had no problems doing a recursive binary search but the assignment specifically says that the method should only take 2 arguments, the list, and the item you are searching for. This is where I am getting a little lost.

public int binarySearch(List<Card> cards, Card key)
{
    int mid = (cards.size()) / 2;
    if(cards.size() == 1) {
        if(key.equals(cards.get(0))) {
            return 0;
        }
    }
    else {
        if(key.equals(cards.get(mid))) {
            return mid;
        }
        else if(key.compareTo(cards.get(mid)) == - 1) {
            return binarySearch(cards.subList(0, mid), key);
        }
        else if(key.compareTo(cards.get(mid)) ==  1) {
            return mid + 1 + binarySearch(cards.subList(mid + 1, cards.size()), key);
        }
    }
    return -1;
}

因此，除非我搜索不存在的东西并且它属于列表的上半部分，否则这将正常工作.因为我只传递2个参数，所以每次递归调用都必须更改列表，但是，如果它位于上半部分，则我不会丢失索引点，因此如果递归调用，则必须在其上添加索引它最终不在上半部分，然后返回-1 +我以前考虑的所有那些索引.有什么办法可以清除所有内容并使它返回-1?任何建议表示赞赏.

So this will work fine unless I am searching for something that doesn't exist and it belongs in the upper half of the list. Because I am only passing through 2 arguments, I have to change the list with each recursive call, however, if it's in the upper half i can't lose my index spot so I have to add those on there with the recursive call, if it ends up not being in the upper half then it returns -1 + all those indexes i was accounting for previously. Is there a way I can clear it all out and make it just return -1? Any advise is appreciated.

推荐答案

您可以使用两种方法，其中一种调用另一种方法. public方法公开您的家庭作业需要的两个参数接口.它还可以检查空参数-这种东西一开始就只需要检查一次.

You could use two methods, where one calls the other. The public method exposes the two parameter interface your homework needs. It can also check for null parameters - the sort of things that only need checking once, right at the beginning.

您的第二个方法是私有的，只能从第一个方法内部调用.这是标准的递归二进制搜索，其中包含所需的任意数量的参数.

Your second method is private and is only called from inside your first method. That is your standard recursive binary search, with as many parameters as you need.

这篇关于仅具有2个参数的递归二进制搜索方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！