Programmer tries to explain binary search to the police

The Picard Maneuver@startrek.website to Programmer Humor@programming.dev – 2507 points –
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Yeah, pigs don't like to be corrected. Or made to look like they don't know what they're doing.

And they absolutely hate ever doing anything about bicycle theft in particular.

I have heard that very often. I wonder if bikes are harder to track down than other property for some reason.

They only care about property loss when it involves rich people.

Which proves that cops really DO actually do their jobs.

Because protecting the property of the rich is the exact core purpose of policing.

Technically it’s maintaining social order. So get back to work menials or be reported to the Enforcers for organized discontent.

Maintaining social order, especially in the form of violent repression against demonstrations, indirectly protects the rich's properties, so all in a day's work.

Given the number of times I've seen cops on police forums and r/protectandserve use terms like "bikefags", I think it's just the typical cop disgust of anything they perceive to be weak or effeminate.

Yeah, I don't get that. Bicycling requires strength and endurance. It exposes you to the elements. Why is sitting in a cushy car something some people think as being more macho? Is it that you're in control of a heavier and more powerful machine?

Bicycling requires strength and endurance.

So does cleaning a house, but that's "women's work".

Is it that you're in control of a heavier and more powerful machine?

That's it. You didn't get it at first because made the mistake of associating manliness with things like patience, strength, hard work, endurance both of toil and hardship; all things that do make up ideals of manliness to normal people. But you need to approach it from the perspective of a wastrel, a weak, foolish, and lazy person who demands the respect and deference of being manly without putting in the hard work—something he has avoided all his life. He might praise hard work in abstract, but he has no discipline for it and doesn't respect those who actually do it, he just considers them beneath him. To such a person, the defining aspect of manliness and machismo is mastery, mastery over others and their wills, and since mastery through work is a waste of time to him, he turns to shortcuts.

From there, it's not hard to see where the thought process goes. Since strength is to him based on control and mastery, he picks something that gives him more command over the road in a direct and in-your-face way. The man who drives a lifted Ram 2500 can confront you by running you the fuck over. By contrast, in his opinion, cyclists are entitled jackasses in miniscule booty shorts who can only confront you on the road by screaming "CRITICAL MASS! FUCKING CAGER!" and throwing sparkplugs at your windows. The difference in power dynamic is proof enough to our friend of who the "real man" is.

To take the mentality to its conclusion, the easiest way to gain mastery in general is through authority, and the easiest way to get that, even easier than joining a gang, is by becoming a cop.

smaller, therefore easier to hide. Not registered with a central authority like, for example, cars.

There’s plenty of cases where they don’t look for cars either.

Or the cops themselves just straight up steal the car themselves.

My wife’s car was ordered to be towed by, according to the impound lot, the police.

Neat thing was that there was no ticket with the car, no police station within 3 miles had a record of a ticket for her or the car, and the area she had parked had no signs that suggested it was illegal to park where she did, nor does the city have any ordinance about overnight parking.

Best we can figure, is a cop or the tow company that works with the city, just decided to tow a car for funsies and the 500 bucks it took to get it out of impound.

The police and every organization associated with them are corrupt to the core.

Reading that I almost had a thought like it must have been a mix-up or something, but no, US police will murder people with less thought, so that type of fuckery is completely expected.

There is bike registration. https://bikeindex.org

It’s helped track down bike trafficking gangs sending bikes to Mexico. The police just don’t care at all

Love bikeindex, I actually got my stolen bike back thanks to that site. It was literally two years later but still, the police wouldn't have even made a report probably in the city I was at, with bike theft so ubiquitous.

I'm pretty sure any petty theft is very hard to track down. Not just bikes, if someone broke into your house and stole some minor things it's almost certainly not gonna get found. Bikes are the same, it's very easy to resell them and repaint, and nobory registers bikes.

Because even if they look for it and find it, whoever is riding just says it theirs and there is literally nothing the police can do unless it was caught on video or there is a meaningful identifying feature like a serial number or something else specific and unique.

Seeing a sketchy guy with a black and red bike with the same bike rack you had isn't enough to prove anything.

If an officer approached me riding my bike around and asked me to prove it's mine, I couldn't either despite not being a thief.

Anything that's not serialized and recorded is basically impossible to find. If you have serial numbers then they can inform local pawn shops, but even then the shops probably aren't checking serials for anything under $500.

And if the thief just sells it on craigslist then no one is checking serials.

I reported my bike stolen in college and I got a call the next day that they had found it parked in front of a nearby church.

It was stolen on a Sunday. I guess someone didn't want to be late to service.

What you're entering the third act of your love story and you have to get to the church in time to break up the wedding and declare your love, what's a little bike theft? The universe will take care of it.

Probably added the theft to the sins they were confessing that day as well.

It probably depends a lot on where you live. My wife's bike got stolen and she was woken up by police coming to check on it (one of the maintenance guys at our apartment noticed a man at 7-Eleven riding it and recognized it; came back running to check if it's indeed missing and called the police). We fully expected the police would do nothing about it (it was the cheapest Walmart bike), but an hour later they called that they found the bike and have the culprit in custody. It did help that the bike was a girly mint green with a wicker basket, so they instantly recognized it when they saw it.

Then again, in San Francisco, when my wife got her car window smashed and wallet stolen (she was late for class and dropped her wallet under the car seat, didn't stop to take it; but it wasn't the wallet that caught the thieves' attention, it was the breast pump bag that looked like a laptop bag; they threw it on the floor when they saw what it was), we never heard anything back from the police.

And they absolutely hate ever doing anything about bicycle theft in particular.

FTFY

Fun fact. Cops on average have lower IQ and often fail literacy tests. Furthermore it appears that critical thinking is discouraged in the job, with candidates being selected who lack critical thinking abilities over those that have them.

We need to have a chat about your definition of "fun".

Certain departments specifically have IQ tests, in order to ensure you aren’t smart enough to easily get a better job elsewhere.

I think it's more nefarious than that. Many departments want a good 'ol boys club where they're the ultimate authority and they want their officers to fall in line rather than question department actions.

This internet myth has got to die. ONE case in ONE department, a quarter century ago, does not mean it's a practice.

https://www.nytimes.com/1999/09/09/nyregion/metro-news-briefs-connecticut-judge-rules-that-police-can-bar-high-iq-scores.html

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This argument did not go well

You can't convince people to do their job with logic when they just don't want to do their job. After minorities, the thing cops hate most is doing their job.

WRONG! After minorities, it's poor people. Then doing their job. :P

Come on, don't disparage our hard-working Boys in blue. Without police who's going to come to your house to take notes about the crime that you have sufficient evidence to prove, and even have a likely suspect for, and then never follow up?

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I thought this had to be hyperbole, so I did the math myself. I'm assuming human history is 200,000 years as google says, and we want to narrow this down to the second the bike disappeared. also that the bike instantly vanished so there's no partially existing bike.

each operation divides the time left in half, so to get from 200k years (6.311×10^12 seconds) to 1 would take ~42.58 divisions, call it 43. even if we take a minute on average to seek and decide whether the bike is there or not it would still be less than an hour of manual sorting

hell, at 60fps it would only take another 6 divisions to narrow it down to a single frame, still under an hour

edit: to use the entire hour we'd need a couple more universes worth of video time to sort through, 36.5 billion years worth to be exact. or a measly 609 million years if we need to find that single frame at 60fps

I regularly bisect commits in the range of 200k (on the low end) for finding causes of bugs. It takes me minutes. Pretty crazy

Lemmy learns exponential math.

Mostly joking, thanks for doing the math.

History is about 10k years, the 200k years is mostly pre-history. People didn't write stuff down until they invented agriculture and needed to track trade between owners, workers, etc

True and interesting to note. OOP says 'dawn of humanity' though, not recorded history, so taking 200k as 'human history' is also valid.

Yeah, I'm used to the narrower meaning of "history", meaning recorded. I like that definition as it lets you differentiate between it and prehistory.

Well, in this case it must have been recorded on video, so could as well start recording before inventing the writing

Combine AI image/visual-pattern recognition and quantum computing, and this search could be completed before it was even started.

A minute to decide if there is a bike in the picture really ?

As a robot, finding bikes in pictures is really hard, okay

Takes time to precisely seek to each timestamp, but really I just meant that an hour was reasonable even with a lazy cop doing the search

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This didn't go down well.

IT consulting pro-tip: Customers would rather pay for your time and expertise, than be made to feel stupid that they didn't think of something so simple themselves.

After working in desktop support for a year after college, I realized that people just wanted their problem solved and to not feel frustrated. That realization made my job immensely easier because I pivoted from copying a file in 30 seconds and walking away to talking to them a little bit and letting them feel good after we were done. My ticket closing speed slowed down a little but people felt better and I consistently got positive feedback.

Dude same here. I usually say stuff along the lines of 'yea it took me forever the first time to figure it out' or 'it's a common issue that a lot of people have, I'll get it sorted in a sec for you no problem'. Make it seem like they're not stupid, regardless of the truth and then fix it, keeps em happy and more willing to cooperate with you as well.

I also talk through what I'm doing and if they show interest I'll teach them so they can fix it in the future, 'ah I've seen this before, took me like a hour to figure it out on my computer, for me it was a chrome update that broke how downloaded files open. Here let me right click the file, and go to open with, we hit Adobe pdf and check the always open with this program button, that should do it let's test it out. OK seems like its good to go. Let me know if you have any more issues'. If they don't show interest then it's no problem.

Are you my kindred spirit!? :P Thats almost exactly what I do too!

My favourite is when someone apologies for not knowing something or having dumb questions. Apart from "there is never a dumb question" because there usually isn't, I typically respond with "if everyone already knew how to do everything, I'd be out of a job" which always seems to go down well.

Some of my favorite help desk moments are those times you get to a be teacher for someone that's genuinely listening and happy to learn.

My go to is usually 'everything is easy if you know how to do it'

When I started in support 15 years ago my boss said: "First you solve the person, then you solve the problem".

He was a good dude.

Same story here, actually. I cut my teeth on internet telephony (modems) support for an ISP. People would call up furious about not being able to connect. I learned that chatting people up during a long Windows reboot did a lot to humanize their struggle and get them to calm down and loosen up. First few times were organic, then I started looking for pretenses to do this, just to bring the temperature down for the rest of the call.

Call centers tell you to empathize but that's not something you can teach. You can either do it or you can't. So they give those terrible scripts, and then some of them require you to speak the scripted lines, even when you know all it does is piss the caller off.

No hears that scripted pablum at the start of call and thinks it's genuine. No one. "I'm sorry to hear your having issues sir, but I'll be happy to assist you." genuinely comes off condescending at this point. They know you know it's scripted, they know you know the representative has to say it, but they make them do it anyway.

Here's what I found doing ISP call center work, and it worked virtually every single time: imply through tone and pointed comments you're as frustrated as the called with how shitty the service and the hardware is. They're never prepared for it, it always catches their anger off guard.

Don't outright say "Yeah, Cox is absolute dog shit, and that POS gateway we make you pay for isn't worth the cost of the the technician we're sending out to 'fix' it." You'll get in trouble for that.

But if you're careful and creative, you can make them appreciate you think that

Just yesterday, I was helping this manager set up a new system of ticket line (the kind where you get a ticket number and wait for it to be called in a panel). He complained that they didn't have a proper printer just for these tickets, so he made the tickets in excel and printed them. To the right of the number, someone would mark the service, from a list of 6.

"Why not use a single letter prefix and print different piles of passwords? (A01, A02, A03; B01, B02, etc)"

That'll use too much paper. We'll also need more tickets than before

"That will use less paper, you can print 2 tickets using the same space. Also, the amount of tickets always depends on the number of people that show up, but you'll have a better idea of which service is being needed each day"

Mr manager didn't like the idea and moved on to another problem.

Eh, it's less intuitive than you might think, as someone who already knows how to do it.

I once had to explain this process to a software engineer who was quite senior to me. The guy wasn't any idiot, he was a pretty competent engineer, he just didn't know this trick.

The cops might even already know how to do it, they just don't want to, because they're cops.

I'm a little surprised the police didn't already know about that method. Seems like they'd encounter enough CCTV footage that'd it'd be standard training.

I once again overestimate the training levels of the police.

They probably do know. They just aren't meant for protecting your personal property

Right.

What they really want to say is "We aren't interested in investigating your personal theft. Things get stolen all the time and we really can't be bothered. You are not important to us."

But they can't say that, so they instead throw out some excuse that puts the onus back on the other person.

You dont quite understand.

They aren't here to protect your property.

Or you, really.

Not unless you have a couple million in assets, then all of a sudden it's all hands on deck, let's get this bicycle back.

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They can, and do, say that.

Edit: just without the you're not important to us part.

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I dunno. "Don't attribute to malice that which can be sufficiently explained by stupidity." I can totally believe that the average police officer has not thought this through. "5 hours of footage! We don't have 5 hours to look for one bike."

And Detective Conan Doyle O'Brien really did just let his bro fuck around and watch porn and even bring a stripper into the station during footage reviewing hours. Of course, Stuart was quite shocked to hear he was not invited to the stag do later that weekend

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I imagine it's utilized in more "serious" investigations and they just can't be arsed for theft.

In the US most their training involves how to be more aggressive veiled as training to be assertive.

It’s a somewhat narrow situation. You won’t always have the object of interest in plain view of a camera. What if it’s behind a door? Well now you do have to scrub through all the footage

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This post just shows that the police rarely if ever review any video as this method would've been learned as a result of repeatedly reviewing video.

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.

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Police try to understand anything challenge (100% impossible) (gone sexual) (gone violent)

I once had a friend who was robbed of all kinds of stuff including a PS3, and that the guy was signed into his Netflix changing account profiles the very same day. I told him he can just get a tracking number by calling Playstation and that the active police officer can use it to track them. Thing is, the officer ghosted him for like 8 months despite having everything they needed to immediately find the exact location of the perpetrator actively using the stolen property.

They don't care really. As has been my experience anyway.

I once had my car window smashed, a mix of gear taken..some was expensive, some was personal to me. I felt violated. Called the police, explained, gave S/Ns to what I could, told them exactly who did it. He didn't give a shit. Actually made me feel like I was wasting his time. I think Seinfeld covered this..

"We'll let you know if we find anything" "Do you ever find anything?" "No"

But oh, my reg is out of date and the plate scanner picked it up? Boom, they really kick it into gear. So that's $130.. i could just go take care of the tags immediately with a friendly warning but now don't even want to. And in the end I end up pretty fucked.

If only they put that effort into other things I just might have gotten my linear power amps back. Props to anyone who knows that product.

We just give all the tools to solve crimes to people who have no idea how to use them, no biggie.

*have a perverse incentive to not know how to use them or to know things about their job generally.

Sat on jury duty. We literally said not guilty because the officer was supposed to follow a process for line ups and they didn't even do the bare minimum. They were like we got out guy

That's how I look for broken mods too. Move half of them into a temp folder, launch the game. If it works, put half of the sorted out ones back. if it doesn't work, remove another half and try again.

This is all fine and good till it's a conflict between two specific mods. Damn you FO4 on PS4, why you gotta be like that?

You would still at least figure out one of the conflicting mods and could look for updates / further information about conflicts.
Edit: On PC that is.

You can put mods on the PS4?

Bethesda made mod workshop worked on the consoles, so you could share the pc made mods.

Small setback that it didn't support script extender, so it was quite limited. Still better than no modding tho.

To add to your answer, Skyrim also supports mods on PS4/5 and there are even a couple really useful ones. Stuff like the Unofficial Skyrim Special Edition Patch exists, for example.

I have had a much better time w Skyrim mods than FO4 on the PS4 as far as stability goes.

I only have it on PS4, and yes there are lots of mods in the workshop. There are obviously limitations.

Every few months I try installing various mods to make what I want out of it, darker nights, flashlight mod, weapon and armour changes for a more hard core experience, etc, and end up with 15 or so mods installed.

Start a new hardcore mode, get just about past diamond city, and the game invariably starts crashing.

No idea which one or ones are causing the issue, and in the end I get annoyed and go play something else.

When I want to see a broken mod, I just surf over to Reddit.

Btw, this is why i have given up on Early Access on Steam; can't disable updates and have to fix your 100 mods then.

I love Steam, but the fact that you cannot permanently disable auto updates for specific titles is definitely infuriating.

"Exactly my point. We will not be investing an hour looking at the footage to pinpoint the time of theft, now get out!"

Show up with a box of donuts.

"Hey, look what I got for us to eat while looking at that tape!"

"Oh, I don't think those donuts will last more than ten minutes here!"

"No problem, I know a way that won't take that long..."

just tell them there is a black man at the moment of theft, they will get on it lickety split!

I'm sure it didn't go well. If it was somehow framed in a sycophantic way where the police were led to believe it was their idea, I'm sure it would have gone better. Wait that might not be too difficult to do.

Na. If it's British police it's just an excuse. All they're there for after all these years of Tory cuts is to give you a reference number so you can make an insurance claim.

Sounds about right. Cops have low iqs

more importantly cops don't actually give a shit about solving crime.

In England the police primarily exist to keep noise down in middle class areas. I assume it's even worse in America

That is their primary purpose here too but it just requires more violence and subjection, Americans are extra noisy.

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It would have taken 5 minutes at most

My Graphics card/ssd wouldn't be able to handle the skipping of such big files

Yeah, even if it was from the beginning of dawn. No need to check out tape before the guy parked his bike.

But thats 5 minutes of killin' time they'll never get back

On my site's security nvr, it takes five minutes just to convince it that you want to search a particular camera

Their method actually does make sense, you just have to remember they aren't cops to solve (boring) crimes like petty theft. Why get it done as efficiently as possible when you can milk it for hours of overtime? 12 hours of footage means 6+ hours of overtime even watching it at x2 speed, and it's the kind of thing you can basically have going on in the background. Cops being willfully ignorant for their own benefit makes sense to me

You know what's even better than milking it for 6hrs of OT? Saying its "to hard" to the victim, going home and then lying about doing 6hrs of OT and getting paid anyway.

Cops lie about OT systemically. Its absolutely rampant. The only consequence they ever get is either a few hrs suspension without pay or fired, and most states are happy to hire them next door immediately so they can do it again.

“This argument didn’t go down well.”

🤣🤣🤣 LMAO

What an awesome punchline, should have been on its own line for more impact.

God damn, whoever came up with that is clever. I would have never come up with that on my own.

Some security camera systems have this built in. They show snapshots of various times where you choose the total period, say 24 hours. Then you glance through the snapshots that are all displayed at once on the screen and click on the last one where your bike was still there. That will then “zoom in” the timeline and show another set of snapshots, though this time within a smaller total time window. Keep clicking on the last panel with the bike, and it will soon show you the clip of the bike being stolen.

Really helpful to find out when something changed.

Yeah, there's no reason it should take an hour no matter how long the tape is.

If you've got 14 billion years, a theft takes a minute, then you need 53 recursion levels of binary search to find the moment of the theft. (14 billion years can be split into about 7.3e15 1-minute segments, 53 levels of binary search allow you to search through 9e15 segments)

That means OP assumed that it'd take 1 minute to decide whether at a certain still frame the theft had already occured or not, to compute the new offset to seek to, and the time it'd take to actually seek the tape to that point.

Not an unreasonable assumption, but a very conservative estimate. Assuming the footage is on an HDD and you've got an automated system for binary search, I'd actually assume it'd take 5 seconds for each step, meaning finding a 1min theft on 14 billion years of footage would take 5 minutes.

According to my napkin math it would take longer than an hour if the tape was ~3.3*10^218 sec long (or three million trillion trillion... (18 trillions) ...trillion years). Assuming you have only have two options to choose between but can pick which alternative in in 5 seconds (2^720) and you want to get down to a 1 minute intervall.

So i mean its not impossible to find a tape long enough though it seems unlikely that we would be so off in our estimates of the age of the universe.

Covert zorb ball carrying remote control toy racecar through the HRV system

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What if you had to guess a number between 0 and 100 and the other person (or an application) only told you if the number is bigger or smaller? That's the form that's usually presented to CS students and most people end up figuring it out on their own. Then the trick is knowing how to generalize it.

Honestly you probably do it already without thinking about it when trying to figure out where you left off a video that you never paused.

Or if you ever had VHS tapes, or so e from of disc media... perhaps a cassette when looking for a particular part of a song.

Maybe not as methodical as perfectly breaking it down into halves of halves, but xlos enough to help you pin point what part you are looking for.

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Without binary search, we would not have search engines today

Works the same for finding a burned out bulb on a string of Christmas lights too.

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Jesus fucking Christ, I know police are dumb, in fact if your IQ is too high you can actually be legally barred from employment as a police officer in the United States of america. Look it up. But fuck incompetence of these Jokers continue to tickle my asshole in a negative way

I did look it up and there is only 1 case from 2000 that set the high bar at 125. it's not really representative of the whole.

I fuckin hate cops as much as the next person but people love to spout this fact, but there is literally only 1 police department ever that has been documented doing this, and it was the one police department in Connecticut.

However the court did in fact rule it was legal, yes.

But the way everyone talks about it you'd think this was some super widespread policy that many departments use. And as far as I can tell there's only ever been the 1 example. It's the same case that every single article about it refers to.

Oh yea this is how I managed to convince our building management company to identify bicycle thieves in our communal garage.

The final project in my instrumentation class was to tune a PID controller for a hot/cold mixing valve. I (CS/ENG) was paired up with an engineering student and a lot of it was throwing parameters in, seeing if weird shit happened, and then turning down or up based on the result. I had a programming final and something else I was supposed to be studying for, so I just started doing a binary search with the knobs. We got the thing tuned relatively fast and my partner acted like I was a wizard.

How do you do a binary search for an open-end scale (are PID params open-end?) and three knobs at the same time when they interdepend in their influence? I need to know since i have a PID tuning on my personal projects plate

It's been ages, but we'd done rough calculations for the three controls so we roughly knew what we needed. Our teacher was big on manually tuning instead of just using formulas since he thought just running numbers "lacked artfulness."

So we grabbed a point and started searching around manually. I think we were just tuning the derivative portion at that point, trying to get a fast response without the system without it going chaotic and noisy.

This is how I look for the best bits in porn

Fast forward half way and see if the woman is still there?

I fast forward half way and pray she still isn't slobbering on some knob at that point and they've gotten down to businesses already.

It's got huge amounts of applicability in many lifestyles and situations that most people never realize until the moment arrives. I once played a fun game that had you guess a number between 1 and 1 Billion with them telling you higher or lower to earn your freedom. Takes a couple of minutes at most.

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A police officer being unable to think in such a fashion is exactly why no one could solve the see-saw riddle on Brooklyn 99.

For those looking for the handout:

person: A B C D E F G H I J K L

round 1: L L L L R R R R — — — -

round 2: L L R R R — — — L R L -

round 3: L R R — — L R — L L — R

This would be easier to parse with a monospaced font. I'm not sure how that works in lemmy so this might take an edit or two...


round 1: L L L L R R R R — — — -

round 2: L L R R R — — — L R L -

round 3: L R R — — L R — L L — R```

Oh i get it. So if in round 1 it tilted down on the right. Round 2 it was even then round 3 it tilted down on the right then it was person G and they are heavier. However if it was reversed and tilted on the left then even then left then it was still person G but they are lighter. Because that pattern only occurs once. This is brilliant. Thankyou to you and the person you corrected the formatting of.

How do you solve that? I saw a solution in the comments where it says to start with numbering all the people and butting 1234 and 5678 on the see saw, then it says if they weight the same then continue and that seems to work. But if they dont weigh the same it doesnt work and it doesnt say what to do in that case.

you can do it like you weight 6v6 then 3v3 then for the last weighing you weight the 2 out of 3.

or you weigh 4v4 to find out which grouping of 4 the light weight person is in, then do 2v2 and 1v1.

You don't know if the person is lighter or heavier yet.

That's not the question. Either the scales balance, and the third is heavier or lighter, or the scales don't balance and you get both answers, but the question is purposely framed this way

I mean that not knowing it is part of the question, and the proposed solution doesn't work without knowing if the person is heavier or lighter.

If you know if the person is heavier or lighter, the question becomes trivial.

The question is to figure out who is different, not how they are different. That takes one more step, half the time.

Yes, I'm aware. But with 12 people you can't simply divvy the groups in threes constantly, because if you weigh and the groups are unequal, then you don't know in which group the different person is (yet). E.g., weighing ABCD - EFGH can tell you the different person is in IJKL if the groups are even, but if they're uneven you don't know in which of the other two groups the different person is.

The question was to find who doesnt weigh the same and if its heavier or lighter. Watch the clip again.

That's easy enough to answer, but he really should work on his grammar. In that case you just do 3 groups of three, weigh two of them. If they're even, the third group is different. Weigh 2 membres of the third group, they'll either be even or one heavier. Weight the last member against the heavier one from step 2 to see if they're even or not for your answer.

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If 1234 and 5678 don't weigh the same youd need 4 seesaws in some cases

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that dawn of humanity is only going to work if the rewind/fast forward is instantaneous.

Also, if I rewind to the Neolithic and I see a bunch of cavemen, sabertooth tigers and a Schwinn chained to a bike rack, I'm not going to just fast forward from there. I have other questions.

They're paid by the hour.

"Yes, chief, I'll need 72h to manually review all 72h of footage and cannot do any other activities in the meantime."

I'm realizing now that this would have been super useful when I worked in Loss Prevention way back when. Wish I had known...

Even without algorithm knowledge it should be fairly obvious that you can just fast forward several minutes and check if the item has gone missing.

Not the most efficient solution, but beats watching the entire tape in real time.

I mean, in the era of VHS this won't work because ultimately you're fast forwarding and rewinding. So you're gonna watch it anyway. but in the digital era I thought this would be what any Police officer did?

Like... they're not even gonna spend 10 minutes on a theft?

my guy half of them don't spend 10 minutes on a murder. There's a reason it's called detective fiction

I know but if they were smart they'd say they're gonna take an hour to do it, find the footage in 10 minutes and goof off another 50.

Pull a Scotty, then you're productive and lazy. It's just disappointing they can't even procrastinate properly. I feel bad.

Like... they're not even gonna spend 10 minutes on a theft?

What and be responsible for paperwork?

Cops are the biggest bludges you’ll ever meet.

In Artillery you call it bracketing/straddling.

It's called bracketing in electrical engineering as well for troubleshooting.

Called half splitting in troubleshooting terms when I was in the Navy.

Half split bracketing was the term I learned in aviation electronic school in the Navy.

That's an analogy that might appeal to the LE types.

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Afterwards I found a chatroom thread among Cambridge computer scientists, one of whom had also been told that unless he could pin down the moment of theft no one would look at the footage. He said he had tried to explain sorting algorithms to police - he was a computer scientist, after all. 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 through. It's very quick. In fact, he had pointed out, if the CCTV footage stretched back to the dawn of humanity it would probably have only taken an hour to find the moment of theft. This argument didn't go down well.

Pfft, didn't even try to enhance the footage. They're obviously not cut out for forensics work.

This student should never go to xitter. Or will be canceled instantly.

Sure, fuck xorg knockoff. What's the connection here, tho?

Binary search. They don't like it.

I do not get why it would work in that case. I assume the scenario is someone with a bike coming, doing theft, then leaving with the same bike.

Therefore there will be a period without bike, then a period with bike, then a period without bike again.

Let's assume there is no bike on the particular moment viewed. How do you know whether it occured before or after the theft? If you make the wrong decision, you get stuck on an endless binary search.. Unless you take note at each timestamp where you made the decision, draw a tree of timestamps, and go back the tree if your search is fruitless but that's much more complicated than what this post says.

You're making this way more complicated than it actually is. The guy definitely can give estimates for when he parked the bike and when he found out that it was stolen. It's not that complicated.

I misunderstood the problem. I thought the thieve came on bike to steal something. I did not get that the bike itself was what got stolen.