在C#中，如何排序该项目列表中哪个项目更大? [英] In C#, how can I order this list of objects by which item is greater?

问题描述

我有一个名为Team的简单类，如下所示:

I have a simple class called Team, that looks like this:

public class Team
{
     public Team ParentTeam;
     public string Name;
}

因此，它有一个名称和对另一个团队(其上级团队)的引用.

So it has a Name and a reference to another team that is its Parent Team.

我现在有一个从功能中返回的团队列表

I now have a list of Teams that I am getting back from a function

List<Team> list = GetTeamsList();

给出一些假设:

1. 除一个团队(顶级团队)外，所有团队都有一个ParentTeam团队
2. 列表中返回的每个团队都是同一层次结构的一部分，并且只有一个层次结构(在同一级别"中没有2个团队)

我现在需要获取此函数的结果并按层次结构对列表进行排序

I now need to take the results of this function and order the list by the hierarchy

因此，假设我们有以下团队信息:

So imagine we have the following team information:

|| Team Name || Parent Team Name ||
||-----------||------------------||   
|| Team A    || Team B           ||   
|| Team B    || Team C           ||   
|| Team C    || Team D           ||   
|| Team D    || null             || 

，但是GetTeamsList()函数以任何随机顺序返回团队.例如，它可能会回来列出以下内容:

but the GetTeamsList() function returns the teams in any random order. For example, it might come back list this:

 var teamA = GetTeamA();
 var teamB = GetTeamB();
 var teamC = GetTeamC();
 var teamD = GetTeamD();

 List<Team> list = new List() { teamD, teamA, teamB, teamC };

我需要在此列表上重新排序，因此它看起来像这样:

where I need to reorder this list so it looks like this:

 List<Team> list = new List() { teamA, teamB, teamC, teamD };

如何根据团队层次结构将列表重新排序为正确"的顺序?

How could I reorder a list into the "correct" order based on the team hierarchy?

推荐答案

到目前为止给出的几个解决方案都是正确，并且它们的团队总数至少都是二次方；随着团队数量的增加，它们将变得效率低下.

Several of the solutions given so far are correct, and all of them are at least quadratic in the number of teams; they will be inefficient as the number of teams grows large.

这是一个到目前为止到目前为止(1)线性，(2)更短，(3)更易于理解的解决方案:

Here's a solution which is (1) linear, (2) shorter, and (3) easier to understand than some of the other solutions so far:

static IEnumerable<Team> SortTeams(IEnumerable<Team> teams)
{
  var lookup = teams.ToDictionary(t => t.ParentTeam ?? new Team());
  var current = teams.Single(t => t.ParentTeam == null);
  do
    yield return current;
  while (lookup.TryGetValue(current, out current));
}

这会按照您想要的顺序产生相反的顺序，因此，如果您希望以其他顺序来排列它，则在通话结束时放置一个Reverse:

This produces the sequence in the reverse of the order you want, so put a Reverse on the end of the call if you want it in the other order:

Console.WriteLine(String.Join(" ", SortTeams(teams).Reverse().Select(t => t.Name)));

虚拟"团队之所以存在，是因为字典不允许键为空.

The "dummy" team is there because a dictionary does not allow a key to be null.

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