Calculate location and number of intersections between multiple date/time ranges?

Question

I need to calculate the location of intersections between multiple date ranges, and the number of overlapping intersections. Then I need to show which date/time ranges overlap each of those intersecting sections. It is slightly more complicated than that so I'll do my best to explain by providing an example. I am working in VB.Net, but C# examples are acceptable as well as I work in both.

We have several high risk tasks that involve the same system. Below I have three example jobs named HR1/2/3/4 with start and end date/times.

• HR1 {1/6/2010 10:00 - 1/6/2010 15:00}
• HR2 {1/6/2010 11:00 - 1/6/2010 18:00}
• HR3 {1/6/2010 12:00 - 1/6/2010 14:00}
• HR4 {1/6/2010 18:00 - 1/6/2010 20:00}

What I want the end result to be is shown below. I am having trouble describing it any way but by example.

• HRE1 {1/6/2010 10:00 - 1/6/2010 11:00} - Intersects 1
• {End Time Split 1, for readability only, not needed in solution}
• HRE1 {1/6/2010 11:00 - 1/6/2010 12:00} - Intersects 2
• HRE2 {1/6/2010 11:00 - 1/6/2010 12:00} - Intersects 2
• {End Time Split 2, for readability only, not needed in solution}
• HRE1 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3
• HRE2 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3
• HRE3 {1/6/2010 12:00 - 1/6/2010 14:00} - Intersects 3
• {End Time Split 3, for readability only, not needed in solution}
• HRE1 {1/6/2010 14:00 - 1/6/2010 15:00} - Intersects 2
• HRE2 {1/6/2010 14:00 - 1/6/2010 15:00} - Intersects 2
• {End Time Split 4, for readability only, not needed in solution}
• HRE2 {1/6/2010 15:00 - 1/6/2010 18:00} - Intersects 1
• {End Time Split 5, for readability only, not needed in solution}
• HR4 {1/6/2010 18:00 - 1/6/2010 20:00} - Intersects 1

Any help would be greatly appreciated.

Answer 1

var timePoints = (from r in ranges select r.Start)
    .Concat(from r in ranges select r.End)
    .Distinct().OrderBy(dt => dt).ToArray();

var intersections = from i in Enumerable.Range(0, timePoints.Length - 1)
                    let start = timePoints[i]
                    let end = timePoints[i + 1]
                    from range in ranges
                    where range.Start <= start && range.End >= end
                    select new { Range = range, Start = start, End = end };

EDIT: Modified code that counts intersections:

var timePoints = (from r in ranges select r.Start)
    .Concat(from r in ranges select r.End)
    .Distinct().OrderBy(dt => dt).ToArray();

var intersectionGroups = from i in Enumerable.Range(0, timePoints.Length - 1)
                         let start = timePoints[i]
                         let end = timePoints[i + 1]
                         select new
                         {
                             Start = start,
                             End = end,
                             Ranges =
                                 from range in ranges
                                 where range.Start <= start && range.End >= end
                                 select range
                         };

var intersections = from intGroup in intersectionGroups
                    let count = intGroup.Ranges.Count()
                    from range in intGroup.Ranges
                    select new
                    {
                        Range = range,
                        Start = intGroup.Start,
                        End = intGroup.End,
                        Count = count
                    };

I don't know what do you want to do with the result, but it may be better to use intersectionGroups rather than intersections.