Question

简单的问题。我有一个有序的日期集合。他们是英国约会btw

01/01/10
01/02/10
01/03/10
01/04/10
02/04/10
03/04/10
04/04/10

我想将其转换为日期范围的集合

01/01/10 -> 01/01/10
01/02/10 -> 01/02/10
01/03/10 -> 01/03/10
01/04/10 -> 04/04/10

为了澄清，我正在尝试将任何连续日期转换为范围。因此，前3个日期是独立的，最后4个日期将转换为4月1日至4月4日的范围。

现在我可以使用循环来做到这一点，但它不是很优雅。有没有人有任何解决方案？

由于

Answer 1

鉴于您要确定连续日期范围的范围，我认为您唯一的选择是，正如您所说的循环。您可以在一次通过中执行此操作，并将其放在扩展方法中，以便它可以在任何IList<DateTime>上运行，例如：

// purely an example, chances are this will have actual, y'know logic in live
public class DateRange
{
    private List<DateTime> dates = new List<DateTime>();

    public void Add(DateTime date)
    {
        this.dates.Add(date);
    }

    public IEnumerable<DateTime> Dates
    {
        get { return this.dates; }
    }
}

public static IEnumerable<DateRange> GetRanges(this IList<DateTime> dates)
{
    List<DateRange> ranges = new List<DateRange>();
    DateRange currentRange = null;

    // this presumes a list of dates ordered by day, if not then the list will need sorting first
    for( int i = 0; i < dates.Count; ++i )
    {
        var currentDate = dates[i];
        if( i == 0 || dates[i - 1] != currentDate.AddDays(-1))
        {
            // it's either the first date or the current date isn't consecutive to the previous so a new range is needed
            currentRange = new DateRange();
            ranges.Add(currentRange);
        }

        currentRange.Add(currentDate);
    }

    return ranges;
}

您还可以传入IEnumerable<DateTime>：

，使其更加通用

public static IEnumerable<DateRange> GetRanges(this IEnumerable<DateTime> dates)
{
    List<DateRange> ranges = new List<DateRange>();
    DateRange currentRange = null;
    DateTime? previousDate = null;

    // this presumes a list of dates ordered by day, if not then the list will need sorting first
    foreach( var currentDate in dates )
    {
        if( previousDate == null || previousDate.Value != currentDate.AddDays(-1) )
        {
            // it's either the first date or the current date isn't consecutive to the previous so a new range is needed
            currentRange = new DateRange();
            ranges.Add(currentRange);
        }

        currentRange.Add(currentDate);
        previousDate = currentDate;
    }

    return ranges;
}

Answer 2

var stringDates = new List<string> {"01/09/10", "31/08/10", "01/01/10"};

var dates = stringDates.ConvertAll(DateTime.Parse);
dates.Sort();

var lastDateInSequence = new DateTime();
var firstDateInSequence = new DateTime();  

foreach (var range in dates.GroupBy(
    d => { if ((d - lastDateInSequence).TotalDays != 1)   
               firstDateInSequence = d;  
           lastDateInSequence = d;
           return firstDateInSequence;  
         }))
    {
        var sb = new StringBuilder();
        sb.Append(range.First().ToShortDateString());
        sb.Append(" => ");
        sb.Append(range.Last().ToShortDateString());
        Console.WriteLine(sb.ToString());
    }

Answer 3

dates.Aggregate(new List<DateRange>(), (acc, dt) =>
                                       {
                                         if (acc.Count > 0 && acc.Last().d2 == dt.AddDays(-1))
                                           acc[acc.Count - 1].d2 = dt;
                                         else
                                           acc.Add(new DateRange(dt, dt));
                                         return acc;
                                       }
    );

其中DateRange是这样的类：

class DateRange
{
  public DateTime d1, d2;

  public DateRange(DateTime d1, DateTime d2)
  {
    this.d1 = d1;
    this.d2 = d2;
  }
}

从日期集合C＃中查找日期范围

3 个答案: