I d like to create a scheduler app that contains a list of e

Question

I d like to create a scheduler app that contains a list of events Each event has a `startDate` and an `endDate` I d like to determine which events overlap so I can place events in a different column Is there a way to apply some sort of `groupBy` function to accomplish a way for me to group them

ephemient · Answer

overlapping ranges are not transitive so this requires a different approach than groupBy

Nick · Answer

Darn Any suggestions

ephemient · Answer

see <https en wikipedia org wiki Interval tree|https en wikipedia org wiki Interval tree>

asad.awadia · Answer

Might also be able to sort by start time and use a stack repurpose this interview question <https www techiedelight com merging overlapping intervals |https www techiedelight com merging overlapping intervals >

Nick · Answer

Oh thanks

andries.fc · Answer

Have a look at this <https gist github com andriesfc 57917aecf460c47c4428a9ddce2148fd>

Nick · Answer

Thanks < andries fc> If I have a list of these ```data class Event val id Int val startDate LocalDate val endDate LocalDate val name String ``` How would I use your function

andries.fc · Answer

Will have a look just in the road

andries.fc · Answer

< Nick> here is simplification for your use case

Nick · Answer

heart heart heart heart heart heart

Nick · Answer

Thanks so much

Nick · Answer

It looks great but I ll try it out tomorrow

andries.fc · Answer

no problem just make sure i ve covered all the edge cases in the `Event overlap ` function before just using it did not write any test cases

ephemient · Answer

a would be much simpler and easier to verify if written as ```fun Event overlap other Event Boolean = startDate lt = other endDate amp amp endDate gt = other startDate``` b there s no reason to use a fold ```val overlappingEvents = buildList for event in events ``` c the approach is just wrong ```val events = listOf Event 1 LocalDate 2022 04 20 LocalDate 2022 04 23 event 1 Event 2 LocalDate 2022 04 20 LocalDate 2022 04 21 event 2 Event 3 LocalDate 2022 04 22 LocalDate 2022 04 23 event 3 sortedBy Event startDate ``` returns two disjoint groups instead of one

ephemient · Answer

it s not that hard to borrow from a naïve interval tree and simplify assuming you only need to build the overlapping structure once not add or make queries later on <https pl kotl in gygTr 6x3> but if you want to be able to add and remove events dynamically you really do need a proper interval tree implementation