c# - 从 List<T> 中选择与无法直接在属性上指定的条件相匹配的组

Question

我有以下指定数据记录的类

class DataRecord
{
    public double MeasuredValue { get; set; }
    public DateTime MeasurementDate { get; set; }
}

我想选择在一小时范围内(日期无关紧要)拍摄的记录，其中拍摄的记录数最多。

示例:

1. 测量日期:2019/01/31 11:50
2. 测量日期:2019/02/02 17:21
3. 测量日期:2019/03/01 17:59
4. 测量日期:2019/03/12 10:54
5. 测量日期:2019/05/28 11:15

预期输出:1, 4, 5(因为在 10:50 - 11:50 范围内进行了 3 次测量)

我想出的代码是

List<DataRecord> records = new List<DataRecord>();
var maxRecordsInAnHour = records.GroupBy(x => x.MeasurementDate.Hour)
                                .Aggregate((g1, g2) => { return g2.Count() > g1.Count() ? g2 : g1; });

此代码返回 2 和 3 或 1 和 5(取决于顺序)，因为我按 Hour 属性进行分组，并且只是Hour 中具有相同值的记录将被分组。

如何调整我的代码以获得预期的输出？

Answer 1

我将为您的问题提出 2 种解决方案，具体取决于您列表的长度，其中一种会更好。

初始化:

var myList = new List<DataRecord>
{
    new DataRecord
    {
        MeasurementDate = new DateTime(2019, 1, 31, 11, 50, 0)
    },
    new DataRecord
    {
        MeasurementDate = new DateTime(2019, 1, 31, 17, 21, 0)
    },
    new DataRecord
    {
        MeasurementDate = new DateTime(2019, 1, 31, 17, 59, 0)
    },
    new DataRecord
    {
        MeasurementDate = new DateTime(2019, 1, 31, 10, 54, 0)
    },
    new DataRecord
    {
        MeasurementDate = new DateTime(2019, 1, 31, 11, 54, 0)
    },
};

List<DataRecord> result = new List<DataRecord>();

解决方案1:

var minimumMinutes = myList.Min(x => x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute);
var maximumMinutes = myList.Max(x => x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute);

for (int minutes = minimumMinutes; minutes < maximumMinutes; minutes++)
{
    var list = myList.Where(x =>
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute <= minutes + 60 &&
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute >= minutes);

    if (result.Count < list.Count())
    {
        result = list.ToList();
    }
}

解决方案2:

foreach (var dataRecord in myList)
{
    var minutes = dataRecord.MeasurementDate.Hour * 60 + dataRecord.MeasurementDate.Minute;
    var before = myList.Where(x =>
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute >= minutes - 60 &&
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute <= minutes).ToList();
    var after = myList.Where(x =>
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute <= minutes + 60 &&
        x.MeasurementDate.Hour * 60 + x.MeasurementDate.Minute >= minutes).ToList();

    if (before.Count > result.Count ||
        after.Count > result.Count)
    {
        result = before.Count > after.Count ? before.ToList() : after.ToList();
    }
}