Find the closest time from a list of times

Question

So, here's the scenario. I have a file with a created time, and I want to choose a time from a list of times that that file's created time is closest or equal too...what would be the best way to accomplish this?

Solution 1

Something like this:

DateTime fileDate, closestDate;
ArrayList theDates;
long min = long.MaxValue;

foreach (DateTime date in theDates)
 if (Math.Abs(date.Ticks - fileDate.Ticks) < min)
 {
   min = Math.Abs(date.Ticks - fileDate.Ticks);
   closestDate = date;
 }

Solution 2

var closestTime = listOfTimes.OrderBy(t => Math.Abs((t - fileCreateTime).Ticks))
                             .First();

If you don't want the performance overhead of the OrderBy call then you could use something like the MinBy extension method from MoreLINQ instead:

var closestTime = listOfTimes.MinBy(t => Math.Abs((t - fileCreateTime).Ticks));

Solution 3

The accepted answer is completely wrong. What you want is something like this:

  DateTime fileDate, closestDate;
  List<DateTime> theDates;

  fileDate = DateTime.Today;       //set to the file date
  theDates = new List<DateTime>(); //load the date list, obviously

  long min = Math.Abs(fileDate.Ticks - theDates[0].Ticks);
  long diff;
  foreach (DateTime date in theDates)
  {
    diff = Math.Abs(fileDate.Ticks - date.Ticks);
    if (diff < min)
    {
      min = diff;
      closestDate = date;
    }
  }

Solution 4

var closestTime = (from t in listOfTimes
                   orderby (t - fileInfo.CreationTime).Duration()
                   select t).First();

Solution 5

How often will you be doing this with the same list of times? If you're only doing it once, the fastest way is probably to just scan through the list and keep track of the closest time you've seen yet. When/if you encounter a time that's closer, replace the "closest" with that closer time.

If you're doing it very often, you'd probably want to sort the list, then use a binary search.

View more solutions