使用linq从列表列表中获取n个项目

Question

我有一个包含其他用户/播放器列表的列表。 这些用户按照他们的特定范围的高尔夫障碍进行分组和分类。 例如，内部列表包含的索引

[0] =>计数2（玩家）

1 =>计数3（玩家）

[2] =>计数1（玩家）

为了在锦标赛中进行飞行，这些玩家/用户被分组为每次飞行最多3或4个玩家。 我如何根据指定的限额填写每个航班。 零索引包含2个玩家，因此我必须从下一个索引中减去其余2个玩家，依此类推以补偿玩家。

对于上述所有情况，我试图使用LINQ查询执行此类功能，但无法解决。 下面是我尝试过的。

List<List<Models.User>> PlayerSortedList = new List<List<Models.User>>(); //contains all the grouped players 

foreach (var item in PlayerSortedList)
{
var extraPlayers = new List<Models.User>();

if (item.Count != Convert.ToInt16(vm.flight.PlayerLimit))
{
//Take extra players from next list and remove players from the next list
 int limit = Convert.ToInt16(vm.flight.PlayerLimit) - item.Count;
 var players = PlayerSortedList.Skip(i); // this has not skipped the first index


 extraPlayers = (from player in players
 from p in player
 where player.Count > 0
 orderby (p.UserHandicap).Take(limit)
 select p).ToList(); // generating error as must be icomparable but i dont 
 have to compare anything, but take out players from the next items in the list
}

通过从列表中的下一个项目中抽出额外的玩家，我确实必须将它们添加到上一个列表中，并从我已删除的列表中删除那些玩家。

Answer 1

那这个呢？

    static void Main(string[] args)
    {
        var listOfListOfPlayers = new List<List<Player>>();
        //Flatten the list, so not having to deal with lists of lists
        var allPlayers = listOfListOfPlayers.SelectMany(l => l).ToList();
        //Count the players that can not take part of a flight
        var playersNotFittingInFlight = allPlayers.Count % 4;
        //The number of players that will be spread in flights
        var maxPlayersInFlights = allPlayers.Count - playersNotFittingInFlight;
        //The number of flights you will end up having
        var maxFlights = maxPlayersInFlights / 4;
        var flights = new List<Flight>(maxFlights);
        //Create the flights with the players
        for (var i=0;i<maxPlayersInFlights; i=i+4)
        {
            var flight = new Flight();
            //Take 4 players everytime.
            var players = allPlayers.Skip(i).Take(4);
            flight.Players.AddRange(players);
            flights.Add(flight);
        }
    }

    public class Flight
    {
        public List<Player> Players { get; set; } = new List<Player>();
    }

    public class Player
    {

    }
}

Answer 2

可以通过使用单个linq查询来做到这一点。

var limit = 4;
var results = playerSortedList
    // Combine all the users in the lists into a single list
    .SelectMany(l => l) 
    // .SelectMany(l => l.OrderBy(x=>x.Handicap)) // use this in case it is needed to reorder the users within each sub list.

    // Use index of the users within the list to create bucket numbers.
    .Select((user, idx) => new { User = user, Bucket = (idx / limit) })

    // Group the users using the bucket numbers.
    .GroupBy(x => x.Bucket)

    // Make the whole thing a List<List<User>> again.
    .Select(x=>x.Select(bucket => bucket.User).ToList())
    .ToList();

亲切的问候，D.