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Let's say I have a list of intervals (or ranges) (Eg. 10-15, 5-7, 9-12..). The problem is to find the subset of ranges that overlaps. Of course I can use Interval tree for this.

The actual problem that I have is there are multiple ranges. Best explained by an example:

  1. 10-15, 5-7, 9-12
  2. 1-2, 3-6, 14-15
  3. 3-5, 9-15, 10-15

In the above case, there is an overlap between (1) and (2) at the second range, and between (3) and (1), (2) at third range.

Basically, I need to find all the overlaps between the list of items.

Maybe I can use 3 separate interval trees to find this out. Is there a better way to do this?

Zifre
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amit
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  • You should think about what you want/need. Do you want to have the ranges that overlap for all 3 or all the ranges that overlap between any two of them? The latter will lead to many results, especially for more than 3 items. – schnaader Mar 17 '09 at 08:19

2 Answers2

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You could build just one interval tree with all intervals in there. You'll just need to keep track of which range the interval belonged to, such as:

{
  int range;
  int intervalFrom;
  int intervalTo;
}

You can put that structure inside an interval tree and check for overlapping. When you get the problematic intervals, you'll be able to tell which range each one belonged to.

Seb
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Intervals [a0, b0] and [a1, b1] overlap iff min(b1,b0) > max(a1,a0)

Devashish Das
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  • Welcome to Stack Overflow! Whilst this may theoretically answer the question, [it would be preferable](//meta.stackoverflow.com/q/8259) to include the essential parts of the answer here, and provide the link for reference. – Enamul Hassan Apr 20 '16 at 00:18