[euphemize]

Interesting. Had a google interview not too long ago, and this was exactly the question asked to me - how would you design an algorithm to find overlapping free time from person X, Y and Z. I guess they got more practical with their questions over the years.

Looks great, liking that is suggests times too.

[CardenB]

Isn't that just a bit wise AND?

[enjo]

There might be a really clever hash you could build, but it's actually a somewhat complex problem. Finding an overlapping range between two entities is easy... finding it for n-entities is a bit more difficult particularly if you want to do it efficiently. I can imagine a couple of answers.. you can build a lookup table (which makes sense if the time resolution is low enough) and then find gaps in it.

It's actually a pretty good interview question if your going to ask a whiteboard question. It has lots of answers depending on requirements. You can get into parallelizing it for speed. It's more of a practical problem than most and you can implement it basically any language.

[karussell]

It is still just a bitwise AND

[TorKlingberg]

Sure, if you store everyones calendars as bitmaps of free minutes, but that seems like a very inconvenient format for other operations.

[dsymonds]

Try having actual time ranges, not just slots, and you need to find, say, a 30m contiguous block of time.

[bobbles]

Also not on weekends, or outside hours during the week, also not at lunch time, though it may be 'free', also not 5PM, who's paying attention to a meeting then?

(just examples of what i might consider when setting up a meeting manually)

[karussell]

It is still just bitwise if you model the time slots e.g. like one bit stands for 5 or 1 minutes and then look for some contiguous 'free'-block in the result

[dsymonds]

Okay, how do you find a string of N 1's in a very long bit pattern? What's the space and time complexity of your solution? (hint: you can do a lot better)