从C＃中的对象列表创建组

Question

I Have a list of objects called Team and I want to create groups of them but not in order, randomized. The groups number is given to the function as well as the list

public List<List<Team>> GenerateGroups(List<Team> teams, int amount)
{
    List<List<Team>> result = new List<List<Team>>();
    for (int i = 0; i < amount; ++i)
        result.Add(new List<Team>());
    foreach(Team team in teams)
    {
        //Add something           
    }
    return result;
}

i got stuck here. I am not sure how to add the teams. Also if someone can condense my code, it will be pretty helpful. I don't need it to return List> if someone has a better idea.

Answer 1

This will order your teams randomly and then put them in groups. The number of output groups in the list is according to the amount parameter:

public static List<List<Team>> GenerateGroups(List<Team> teams, int amount)
{
    return teams.OrderBy(item => Guid.NewGuid())
            .Select((item, index) => new { Item = item, GroupIndex = index % amount })
            .GroupBy(item => item.GroupIndex, 
                     (key, group) => group.Select(groupItem => groupItem.Item).ToList())
            .ToList();
}

---

One can also random using the Random class but I would use it to create the order and not group by it. Like this:

public static List<List<Team>> GenerateGroups(List<Team> teams, int amount)
{
    Random random = new Random();
    return teams.OrderBy(item => random.NextDouble())
            .Select((item, index) => new { Item = item, GroupIndex = index % amount })
            .GroupBy(item => item.GroupIndex,
                     (key, group) => group.Select(groupItem => groupItem.Item).ToList())
            .ToList();
}

Answer 2

I think it's better for you to define Group class like:

class Group {
   List<Team> teams;
}

And about adding teams:

Random rnd = new Random();
List<Group> groups = new List<Group>();
        for (int i = 0; i < amount; ++i)
            groups.Add(new Group());

        foreach(Team team in teams)
        {
            int index = rnd.Next(0, amount);
            groups[index].Add(team);
        }
        return groups;

Answer 3

This one gives random groups without duplicates:

private static Random _rnd = new Random();

private static Team GetAndRemoveRandomTeam(List<Team> allTeams)
{
    int randomIndex = _rnd.Next(allTeams.Count);
    Team randomTeam = allTeams[randomIndex];
    allTeams.RemoveAt(randomIndex);
    return randomTeam;
}

public static List<List<Team>> GenerateGroups(List<Team> teams, int amount)
{
    int teamCount = (int) teams.Count/amount;
    List<Team> allteams = teams.ToList(); // copy to be able to remove items

    if (teamCount == 0)
        return new List<List<Team>> {allteams};

    List<List<Team>> allTeamGroups = new List<List<Team>>();
    List<Team> thisTeam = new List<Team>();
    while (allteams.Count > 0)
    {
        if (thisTeam.Count == amount)
        {
            allTeamGroups.Add(thisTeam);
            thisTeam = new List<Team>();
        }
        thisTeam.Add(GetAndRemoveRandomTeam(allteams));
    }
    allTeamGroups.Add(thisTeam);

    return allTeamGroups;
}