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Programmer tries to explain binary search to the police (startrek.website)

submitted 2 years ago by The_Picard_Maneuver@startrek.website to c/programmer_humor@programming.dev

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[-] CosmicCleric@lemmy.world 3 points 2 years ago* (last edited 2 years ago)

But you will see the event happen though.

Not with a binary search.

Yes you will.

A binary search is just what it says, it's just for searching only.

When you find that moment in time where the bike was there one moment, and then the next moment the bike's not there, then you view at regular or even slow-mo at those few seconds of the bike in the middle of disappearing, and see the perpetrator, and hopefully can identify them.

[-] Azzu@lemm.ee 33 points 2 years ago* (last edited 2 years ago)

You didn't get what was talked about here. Re-read the topmost parent comment.

How do you binary search for two people arriving, one punches the other, they both leave?

[-] CosmicCleric@lemmy.world 2 points 2 years ago* (last edited 2 years ago)

You didn’t get what was talked about here. Re-read the topmost parent comment.

I was responding to this ...

Part of my job is to review security footage for reported incidents.

If there is a long-lasting visual cue that the event has or has not happened yet (e.g. a window is either broken or not), then a binary search is very useful.

If the event lasts only a moment and leaves no visual cue (e.g. an assault), then binary search is practically useless.

I disagree with the "leaves no visual cue" part, as I've commented on. There's ALWAYS something caught on the video to help determine things. Maybe not enough, but never nothing.

[-] LUHG_HANI@lemmy.world 7 points 2 years ago

Maybe I'm not understanding both arguments here but I'd like to understand. I've had to review footage of a vending machine being shaken to release drinks.

You have no before or after visual clue as to when the event took place. The only indication is when you physically see it happening. The same could be said for an assault. If nothing is changed in the before or after static still how can you pinpoint the incident?

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[-] ShrimpsIsBugs@programming.dev 13 points 2 years ago

You either don't know what binary search is or you completely missed the context of this conversation

[-] CosmicCleric@lemmy.world 2 points 2 years ago* (last edited 2 years ago)

You either don’t know what binary search is or you completely missed the context of this conversation

I'm a computer programmer. I know exactly what a binary search is. I've written binary searches before.

The search is to get you to the point where you can watch the video to see the crime happening, in hopes of indentifying the perpretrator.

[-] SkippingRelax@lemmy.world 15 points 2 years ago

Then you missed the point of this conversation

[-] CosmicCleric@lemmy.world 3 points 2 years ago* (last edited 2 years ago)

Then you missed the point of this conversation

You're being intellectually dishonest, in an attempt to kill the message.

This is what was said in the origional OP pic...

You don’t watch the whole thing, he said. You use a binary search. You fast forward to halfway, see if the bike is there and, if it is, zoom to three quarters of the way through. But if it wasn’t there at the halfway mark, you rewind to a quarter of the way though. Its very quick. In fact, he had pointed out, if the CCTV footage stretched back to the dawn of humanity it would probably have taken an hour to find the moment of theft.

[-] WoahWoah@lemmy.world 10 points 2 years ago* (last edited 2 years ago)

Yes, but, as you noted in an earlier post, that isn't what you're responding to. The point of the post you stated you are responding to is: if an event occurs that leaves no change to the visual context before and after the occurrence, then binary search is ineffective.

The fact that you're wasting this much time trying to defend such a simple error is confusing. The reasonable response is, "oh, yes, in that particular case, binary search is ineffective."

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[-] lustyargonian@lemm.ee 12 points 2 years ago

Binary search only works on sorted data, i.e. you know which side of the mid point is pointing towards the incident. If the incident leaves no trail, you can't know whether you can discard the left side or the right side, making it a complicated linear search at that moment.

[-] CosmicCleric@lemmy.world 2 points 2 years ago

If the incident leaves no trail, you can’t know whether you can discard the left side or the right side

There's a moment where the bike is there, then another when its not. The whole video, either way, will either from the beginning up to the point of theft have the bike there, or NOT have the bike there from the point of theft to the end of the video. The marker is the removal of the bike from the video lens.

[-] starman2112@sh.itjust.works 9 points 2 years ago

But the comment you replied to wasn't talking about bike thefts specifically, it was talking about unspecified situations that don't leave traces. You responded to someone saying that binary search doesn't work in situations that don't leave cues not by arguing against the premise (e.g. "but no such event exists, everything leaves cues"), but by telling them that you simply have to look for the cues from the hypothetical event that didn't leave any.