我有有一个部分顺序关系，我的项目清单。即，该列表可以考虑偏序集。我想这个名单以同样的方式进行排序在本问题。作为正确回答有，这被称为拓扑排序。
I have a list of items that have a partial order relation, i. e, the list can be considered a partially ordered set. I want to sort this list in the same way as in this question. As correctly answered there, this is known as topological sorting.
有一个相当简单的公知的算法来解决这个问题。我想一个LINQ般的实现了。
There's a reasonably simple known algorithm to solve the problem. I want a LINQ-like implementation of it.
我已经尝试过使用排序依据扩展方法，但我敢肯定它是不是能够使拓扑排序。问题是，的IComparer＆LT; TKEY的＆GT; 接口是不能够再present部分订单。这是因为比较方法可以返回值的主要三种：零 负和正，这意味着是相等 是-小于和是-更大，那么，分别。一个可行的解决方案只会是可能的，如果有一种方法返回的是无关的
I already tried to use OrderBy extension method, but I'm quite sure it's not able to make topological sorting. The problem is that the IComparer<TKey> interface is not able to represent a partial order. This happens because the Compare method can return basically 3 kinds of values: zero, negative, and positive, meaning are-equal, is-less-than, and is-greater-then, respectively. A working solution would only be possible if there were a way to return are-unrelated.
这是我的偏见的观点，我在寻找通过 IPartialOrderComparer＆LT可能会组成的回答; T＆GT; 接口和一个像这样的扩展方法：
From my biased point of view, the answer I'm looking for might be composed by an IPartialOrderComparer<T> interface and an extension method like this:
public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IPartialOrderComparer<TKey> comparer
);
这将如何实施？如何在 IPartialOrderComparer＆LT; T＆GT; 界面会是什么样子？你会推荐一种不同的方法？我渴望看到它。也许有一个更好的方式来重新present偏序，我不知道。
How would this be implemented? How does the IPartialOrderComparer<T> interface would look like? Would you recommend a different approach? I'm eager to see it. Maybe there's a nicer way to represent the partial order, I don't know.
推荐答案
我会建议使用相同的IComparer接口，但写扩展方法，以便跨preT 0为不相关。在偏序，若元素a和b是相等它们的顺序并不重要，像明智的，如果他们是无关的 - 你只需要订购他们就与他们所定义的关系元素
I would suggest using the same IComparer interface, but writing the extension method so as to interpret 0 as not related. In a partial ordering, if elements a and b are equal their order doesn't matter, like-wise if they are unrelated - you only have to order them with respect to elements with which they have defined relationships.
下面是一条什么偶数和奇数的偏序的一个例子：
Here's an example that does a partial ordering of even and odd integers:
namespace PartialOrdering
{
public static class Enumerable
{
public static IEnumerable<TSource> PartialOrderBy<TSource, TKey>(this IEnumerable<TSource> source, Func<TSource, TKey> keySelector, IComparer<TKey> comparer)
{
List<TSource> list = new List<TSource>(source);
while (list.Count > 0)
{
TSource minimum = default(TSource);
TKey minimumKey = default(TKey);
foreach (TSource s in list)
{
TKey k = keySelector(s);
minimum = s;
minimumKey = k;
break;
}
foreach (TSource s in list)
{
TKey k = keySelector(s);
if (comparer.Compare(k, minimumKey) < 0)
{
minimum = s;
minimumKey = k;
}
}
yield return minimum;
list.Remove(minimum);
}
yield break;
}
}
public class EvenOddPartialOrdering : IComparer<int>
{
public int Compare(int a, int b)
{
if (a % 2 != b % 2)
return 0;
else if (a < b)
return -1;
else if (a > b)
return 1;
else return 0; //equal
}
}
class Program
{
static void Main(string[] args)
{
IEnumerable<Int32> integers = new List<int> { 8, 4, 5, 7, 10, 3 };
integers = integers.PartialOrderBy<Int32, Int32>(new Func<Int32, Int32>(delegate(int i) { return i; }), new EvenOddPartialOrdering());
}
}
}
结果：4,8，3，5，7，10
Result: 4, 8, 3, 5, 7, 10
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