Get breaks from a list of times
algorithm, c#, datetime, time, timespan
Solution
Create pairs of (time, value), where value is +1 for begining of work and -1 for end. Then sort the pairs by date. Iterating the list you got, you can calculate the sum of values - when it is positive, the work is "going on". While iterating, mark the moments when sum of values goes from 0 to positive and from positive to 0. You will get disjoint intervals.
Example:
11 - 13, 12 - 16, 15 - 17, 18 - 19
gives you (11, 1) (12, 1) (13 -1) (15, 1) (16, -1) (17, -1) (18, 1) (19, -1)
the sum goes (11, 1) (12, 2) (13 1) (15, 2) (16, 1) (17, 0) (18, 1) (19, 0),
so the disjoint periods are (11, 17) and (18, 19)
Problem
I have a list of work items. Each work item has a start and an end time. So, basically it looks like this: ``` List<Work> works = new List<Work>(); works.Add(new Work( new DateTime(2013, 4, 30, 9, 0, 0), new DateTime(2013, 4, 30, 11, 0, 0)); ``` Now I want to get the total time that was worked. Again, basically this is easy: ``` 09:00-11:00 => 2 hours 13:00-17:00 => 4 hours ---- 06:00 hours ``` It's just the sum. But now it gets difficult: How do I calculcate this sum if I want to extract parallel times? E.g., ``` 09:00-11:00 => 2 hours 10:00-11:30 => 1.5 hours 13:00-17:00 => 4 hours ---- 06:30 hours ``` is 6.5 hours, but the sum is 7.5 hours. The fact that two work items map to the time between 10 and 11 o'clock makes the difference. How could I solve this for an arbitrary number of work items that can overlap each other in basically every possible way (surrounding, start overlaps, end overlaps, including)?