如何从“不相交的集合”所有的元素列表 [英] How to get list of all elements from a 'Disjoint Sets'

问题描述

在我的问题，我有一大堆的元素（类元素）。说我有1000元。这些元素是最初无关联的，这意味着他们在自己套。

In my problem, I have a bunch of Elements (Class Element). Say I have 1000 Elements. These Elements are initially un-associated which means they are in their own sets.

后来，我需要使用union操作合并一些基于我的程序流程，这些套。
我打算使用Boost库的disjoint_set（ HTTP：// WWW。 boost.org/doc/libs/1_57_0/libs/disjoint_sets/disjoint_sets.html ）

Later I need to use the union operation to merge some of these sets based of my program flow. I plan to use the boost library's disjoint_set (http://www.boost.org/doc/libs/1_57_0/libs/disjoint_sets/disjoint_sets.html)

我的问题是怎么可能列出给出的一组重新presentative一组元素。

My question is how is it possible to list the Elements in a set given the representative of the set.

时disjoint_set用于这种任务的最佳数据结构。所以，我应该考虑用别的东西？

Is disjoint_set the best data structure for such a task. So should I look into using something else?

推荐答案

从你的文字描述，我没有得到任何信息，该套实际上形成任何图形。

From your prose description, I get no information that the sets would actually form any graphs.

如果你想要做的就是联想的元素与一组，我建议

If all you want to do is associate Elements with a set, I'd suggest

std::map<ElementId, SetId>

（其中 ElementId 可能仅仅是元素* 如果你知道指针仍然有效）。

(where ElementId could simply be Element* if you know the pointers stay valid).

如果您还希望能够有效地查询逆

If you also want to be able to query the inverse efficiently

bimap<Element, bimaps::multiset_of<SetId> >

将是一个候选人。看到一个示范<罢工> 住在Coliru ¹

#include <boost/range/iterator_range.hpp>
#include <boost/bimap/multiset_of.hpp>
#include <boost/bimap.hpp>
#include <iostream>

using namespace boost;

int main() {
    using Element = int; // for simplicity :)
    using SetId   = int;
    using Sets = bimap<Element, bimaps::multiset_of<SetId> >;

    Sets sets;
    sets.insert({ Element(1), 300 });
    sets.insert({ Element(2), 300 });
    sets.insert({ Element(3), 400 });
    sets.insert({ Element(4), 300 });

    // give us set #300
    for (auto& e : make_iterator_range(sets.right.equal_range(300)))
        std::cout << e.first << " - Element(" << e.second << ")\n";
}

打印

300 - Element(1)
300 - Element(2)
300 - Element(4)

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¹Coliru似乎下来。之后会添加

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¹ Coliru seems down. Will add later

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