寻找所有兼容元素的可能组合

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英文:

Find all possible combinations of compatible elements

问题

我设置了

{A,B,C,D,E}

并且我有一个表示元素是否兼容的集合映射(在代码示例中为 someMapWithSets):

A: B,C -(表示 A 与 B、C 等兼容)
B: A,E,C
C: A,B
D: E
E: B,D

我需要一个包含所有可能的兼容元素组合的集合映射(尽可能大的集合),其值如下(不关心键):

A,B,C
B,E
D,E

因此,作为解决方案的一部分,我考虑创建一个方法,仅保留给定集合和选定元素的兼容元素。

public static Map<String, Set<String>> defineCompatibility(Set<String> set) {
    if (set.isEmpty()) {
        return new HashMap<>();
    }
    Map<String, Set<String>> finalResult = new HashMap<>();
    Set<String> elementsToDefine = new HashSet<>(set);
    while (!elementsToDefine.isEmpty()) {
        String currentElement = elementsToDefine.stream().findFirst().get();
        Set<String> definedSet = defineForElement(set, currentElement);
        finalResult.put(currentElement, definedSet);
        elementsToDefine.remove(currentElement);
    }
    return finalResult;
}

private static Set<String> defineForElement(Set<String> set, String rootElement) {
    Set<String> result = someMapWithSets.get(rootElement);
    result.retainAll(set);
    result.add(rootElement);
    Set<String> tmpHolder = new HashSet<>(result);
    for (String next : tmpHolder) {
        if (!result.contains(next)) {
            break;
        }
        Set<String> strings = someMapWithSets.get(next);
        strings.add(next);
        result.retainAll(strings);
    }
    return result;
}

但是,这段代码无法正常工作,因为它不能定义所有可能的组合,只能定义其中的一些。我尝试过存储未处理的元素的数据,但代码变得非常复杂,难以理解。

我陷入了实现中。请帮忙。也许有一些这个任务的众所周知的算法?谢谢。

英文:

I have set

{A,B,C,D,E}

And I have a map (someMapWithSets in the code example) of sets which indicates if elements are compatible:

A: B,C - (means A is compatible with B and C and etc) 
B: A,E,C
C: A,B
D: E
E: B,D

I need to have a map of sets where all possible combinations of compatible elements are present (largest set possible) with values like (don't care about key):

A,B,C
B,E
D,E

So as I part of the solution I thought I could create a method that retains only compatible elements for the given set and chosen element.

public static Map&lt;String, Set&lt;String&gt;&gt; defineCompatibility(Set&lt;String&gt; set) {
    if (set.isEmpty()) {
        return new HashMap&lt;&gt;();
    }
    Map&lt;String, Set&lt;String&gt;&gt; finalResult = new HashMap&lt;&gt;();
    Set&lt;String&gt; elementsToDefine = new HashSet&lt;&gt;(set);
    while (!elementsToDefine.isEmpty()) {
        String currentElement = elementsToDefine.stream().findFirst().get();
        Set&lt;String&gt; definedSet = defineForElement(set, currentElement);
        finalResult.put(currentElement, definedSet);
        elementsToDefine.remove(currentElement);
    }
    return finalResult;
}

private static Set&lt;String&gt; defineForElement(Set&lt;String&gt; set, String rootElement) {
    Set&lt;String&gt; result = someMapWithSets.get(rootElement);
    result.retainAll(set);
    result.add(rootElement);
    Set&lt;String&gt; tmpHolder = new HashSet&lt;&gt;(result);
    for (String next : tmpHolder) {
        if (!result.contains(next)) {
            break;
        }
        Set&lt;String&gt; strings = someMapWithSets.get(next);
        strings.add(next);
        result.retainAll(strings);
    }
    return result;
}

But this code does not work properly because it is not capable to define all possible combinations, only a few of them. I've tried to store data about elements that were not processed but the code became very complex to be understandable.

I am stuck with implementation. Please help. Maybe there is some well-known algorithm for this task? Thank you.

答案1

得分: 0

Bron-Kerbosch在结果中使用。

链接:https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm

链接:https://iq.opengenus.org/bron-kerbosch-algorithm/

暴力解法的代码如下:

private static void define(Set<String> r, Set<String> p, Set<String> x) {
    if (p.isEmpty() && x.isEmpty()) {
        System.out.println("Here is maximal clique: " + r);
        return;
    }
    Set<String> p1 = new HashSet<>(p);
    for (String v : p) {
        r.add(v);
        define(r, intersect(p1, someMapWithSets.get(v)), intersect(x, someMapWithSets.get(v)));
        r.remove(v);
        p1.remove(v);
        x.add(v);
    }
}

private static Set<String> intersect(Set<String> first, Set<String> second) {
    Set<String> holder = new HashSet<>(first);
    holder.retainAll(second);
    return holder;
}

请注意,我已经按照您的要求将内容进行了翻译。如有任何问题,请随时提问。

英文:

Bron-Kerbosch is used in result.

https://en.wikipedia.org/wiki/Bron%E2%80%93Kerbosch_algorithm

https://iq.opengenus.org/bron-kerbosch-algorithm/

Brute force code looks like this

private static void define(Set&lt;String&gt; r, Set&lt;String&gt; p, Set&lt;String&gt; x) {

    if (p.isEmpty() &amp;&amp; x.isEmpty()) {
        System.out.println(&quot;Here is maximal clique: &quot; + r);
        return;
    }

    Set&lt;String&gt; p1 = new HashSet&lt;&gt;(p);

    for (String v : p) {
        r.add(v);
        define(r, intersect(p1, someMapWithSets.get(v)), intersect(x, someMapWithSets.get(v)));
        r.remove(v);
        p1.remove(v);
        x.add(v);
    }
}

    private static Set&lt;String&gt; intersect(Set&lt;String&gt; first, Set&lt;String&gt; second) {
    Set&lt;String&gt; holder = new HashSet&lt;&gt;(first);
    holder.retainAll(second);
    return holder;
}

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  • 本文由 发表于 2020年10月2日 00:27:08
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