How to get overlap range of two range

Question

I have the following ranges in interval [1-15]

I want to find the overlap ranges between people 1 & 2.

Person1 [1, 3] [5, 10] Person2 [2, 4] [8, 15]

Answer 1

Sort the starts and ends of the ranges.. keeping information alongside as to whether its a range-start or finish... for your example you'll get this:

1 start
2 start
3 end
4 end
5 start
8 start
10 end
15 end

Now loop over these points and keep a counter.. +1 for a start -1 for an end. This counter is the number of overlapping segments at any time. If you want the boundaries you need to test each time you increase or decrease the counter. If you increase it from 1 to 2 this is a start of an overlapping range.. the end of the overlapping range will be when you decrease the counter from 2 to 1

Martin