c# - 根据组数从列表中均匀选择？

Question

我有一个包含 20 个项目的颜色列表:

this.colors = new List<Color> {
    (Color)ColorConverter.ConvertFromString("#DEEBF7"),
    (Color)ColorConverter.ConvertFromString("#D2E1EF"),
    (Color)ColorConverter.ConvertFromString("#C7D7E8"),
    (Color)ColorConverter.ConvertFromString("#BCCDE0"),
    (Color)ColorConverter.ConvertFromString("#B0C3D9"),
    (Color)ColorConverter.ConvertFromString("#A5B9D2"),
    (Color)ColorConverter.ConvertFromString("#9AAFCA"),
    (Color)ColorConverter.ConvertFromString("#8FA6C3"),
    (Color)ColorConverter.ConvertFromString("#839CBC"),
    (Color)ColorConverter.ConvertFromString("#7892B4"),
    (Color)ColorConverter.ConvertFromString("#6D88AD"),
    (Color)ColorConverter.ConvertFromString("#627EA5"),
    (Color)ColorConverter.ConvertFromString("#56749E"),
    (Color)ColorConverter.ConvertFromString("#4B6B97"),
    (Color)ColorConverter.ConvertFromString("#40618F"),
    (Color)ColorConverter.ConvertFromString("#355788"),
    (Color)ColorConverter.ConvertFromString("#294D81"),
    (Color)ColorConverter.ConvertFromString("#1E4379"),
    (Color)ColorConverter.ConvertFromString("#133972"),
    (Color)ColorConverter.ConvertFromString("#08306B")
};

我将一个列表传递给 GetColors，按 double 值排序和分组:

public SortedDictionary<Guid, Color> GetColors(IList<Tuple<Guid, double>> heightsAboveGroundByGuid)
{
   // Order providers by measurement height from ground
   IEnumerable<IGrouping<double, Tuple<Guid, double>>> groupedOrderedList = heightsAboveGroundByGuid.OrderBy(h => h.Item2).GroupBy(o => o.Item2);

   int numberOfGroups = groupedOrderedList.Count();

   SortedDictionary<Guid, Color> seriesColorsByGuid = new SortedDictionary<Guid, Color>();       

   int index = 0;
   foreach (IGrouping<double, Tuple<Guid, double>> item in groupedOrderedList)
   {
        if (index <= this.colors.Count() - 1)
        {
            foreach (Tuple<Guid, double> childItem in item)
            {
                seriesColorsByGuid.Add(childItem.Item1, this.colors[index]);
            }                   
        }

        index = Not sure how to implement this!;
   }

   return seriesColorsByGuid;
}

例如，在运行时传入的 double 值是 40、40、40、50、50、60、60。因此，我有 3 个小组。在这种情况下，我希望第一组 (40) 返回索引为 0 的颜色，第二组 (50) 索引为 9，最后一组 (60) 索引为 19(列表中的最后一种颜色)。

如何根据传入的组数设置均匀间隔的颜色？

Answer 1

你有以下情况(3、4、5组):

0 --- x_i ---19
0 --- x_i ---x_ii --- 19
0 --- x_i ---x_ii --- x_iii --- 19
etc..

其中 --- 是偶数(左右)间隙，x_n 是您要查找的数字。

这样布局，显然有 3 个组时有 2 个间隙，有 4 个组时有 3 个间隙，有 n 个组时有 n-1 个间隙。因此，您可以将颜色数除以组数，每次都将其添加到索引中。以下代码应该可以满足您的需求。我在每一行新代码之前添加了注释:

public SortedDictionary<Guid, Color> GetSeriesColors(IList<Tuple<Guid, double>> heightsAboveGroundByGuid)
{
    IEnumerable<IGrouping<double, Tuple<Guid, double>>> groupedOrderedList = heightsAboveGroundByGuid.OrderBy(h => h.Item2).GroupBy(o => o.Item2);

    int numberOfGroups = groupedOrderedList.Count();

    SortedDictionary<Guid, Color> seriesColorsByGuid = new SortedDictionary<Guid, Color>();

    int index = 0;

    //calculate the size of the gaps.
    float gap = (this.colors.Count() - 1) / (float)(numberofGroups - 1);
    //keep track of how many multiples of gap we need
    int gapsUsed = 1;

    foreach (IGrouping<double, Tuple<Guid, double>> item in groupedOrderedList)
    {
        if (index <= this.colors.Count() - 1)
        {
            foreach (Tuple<Guid, double> childItem in item)
            {
                seriesColorsByGuid.Add(childItem.Item1, this.colors[index]);
            }
        }
        //set the index to the gap * gapsUsed and cast it to an int
        index = (int)(gap * gapsUsed);
        //increment gaps used
        gapsUsed++;
    }

    return seriesColorsByGuid;
}