Honestly, this was the comment that exposed me (regular office rube) to binary search as a concept and it is so. fucking. helpful.
this post was submitted on 02 Dec 2024
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Man, as someone who worked surveillance for years, I can’t believe that anyone would have a hard time with this.
It was so, so, so, so easy to find when something vanished.
Now, did so and so walk in the building? Yeah, kiss my ass. Not happening.
I worked at a major outdoors retailer with a "gun library" of high-end firearms.
In one of our quarterly steel audits (where we pull all 10,000 guns put hands on them, verify the serials, etc) we discovered a $10,000 rifle was missing.
The thing is, the case it was in obscured the gun itself from the security cameras. It was behind like 6 other guns in a glass case any customer could item and pull the guns out to look at them (guns themselves were trigger-locked of course).
So we had to have the gun library manager sit there and watch 3 month's of surveillance video of a specific case that was proclaimed opened 20 times an hour in a highly-trafficked area of the store. Because of all the activity, the video had to be watched in real time, and we were open 13 hours a day.
The manager ended up quitting over the boredom combined with stress.
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There's a similar logic applied to fault finding, start at the middle of the circuit.
If the fault is before that point, start at the quarter point, if it's after, three quarters, and keep splitting until you find it.
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My bike was stolen, and I live in a small enough town that the cops actually did go through the footage to find the thief.
He called back 15 minutes later for more details and mentioned he was 15 minutes into the footage.
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Pigs are threatened by anyone that's even slightly intelligent
My dad once told me that he had to find the circuit breaker that corresponded to a particular wire and because we have around 60 circuit breakers in our house, he had to flick one off, run down and check the wire, run back up, flick the next circuit breaker off, and do that quite a lot of times.
In that moment, I got to explain binary search to him and he was genuinely interested. 🙃
I think the old school method was to plug in a stereo and turn the volume up. When you couldn't hear it then you got the right breaker.
I hook a cheap webcam up to a USB battery pack and load it up on my phone. Then I plug in a light and point the camera at that. It makes it a single trip and doesn't bother the neighbors.
Binary search only works if the fuses were correctly sorted in the same order as the houses though.
You know, after posting that comment, I really doubted myself, if it really is binary search, because Wikipedia also tells me it needs to be a sorted array.
But yeah, I think that's only relevant, if your method of checking whether it's in one half or the other uses > and <. As far as I can tell, so long as you can individually identify the fuses, a.k.a. they're countable, then you can apply binary search.
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I don't think that's true, it's more of a set problem. If you pull half the fuses, and the thing is still on, then you've ruled out that half. Then you pull half the remaining fuses, and if it turns off it was one of the new half you pulled. Then you put another half back in, ect .
Ah, I didn't think of it that way. That indeed would work.
My friend has some upcoming electrical work in his house, can you explain how to use binary search in this instance so I can tell him?
Oh, well, you switch off half the fuses, then you go check the wire.
Let's say the wire still has power on it, so now you know that none of the fuses in that half affected it (which you can turn back on now).
Then you do the same thing again with the other half of the fuses, i.e. you switch off half of the fuses in that half and go check the wire.
Now, let's say the wire is dead, so now you know that the fuse you want is in this quarter.
So, then you flick off half of the fuses in that quarter and check the wire again, and so on.
With every step, you eliminate half of the remaining fuses, so for 60 fuses, you need at most 6 steps (which is the logarithm for base 2 of 60).
Ah, obvious now, thank you. For some reason ~~my~~ his brain couldn't get to actually turning off half the breakers in one go
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Once you figure out which one it is, label it! I labeled all the breakers in my panel when I moved in to my house, as half of the existing labels were wrong (no idea why).
I keep a spreadsheet with every outlet/light in every room on it and their corresponding breakers. Much easier since breakers often span multiple rooms, sometimes only powering one or two fixtures in each.
That's the case with virtually every breaker box.
Why are so many mislabeled though? It's not like the loads are being changed every day. I had two breakers labeled "dishwasher" and neither of them were the dishwasher!
What Rumba said. Why full ass a job when half is plenty.
I had two breakers labeled “dishwasher”
Electrical work is one of those things that's not difficult to do as long as you don't mind it being some level of wrong but relatively hard to do 100% to code right without training. With most of the wrong ways, the project still works, but it's dangerous and/or hard to maintain. Professional work is expensive, so you end up with a LOT of handyman work that's poorly labeled, poorly run, poorly designed or some combination of the three.
My best guess would be that at some point, running the dishwasher tripped the breaker. They had space so they added a breaker below it and moved the line to the new breaker. Then it still tripped, so they moved the line at the dishwasher circuit that was already close by.
Either the original line has a fault in it (old aluminum lines can have junction issues over time) or the dishwasher had a short in it, and they either replaced the dishwasher, or the new line they chose didn't fail.
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Turn off half the breakers. See if you still have power where you need to go. That will tell you which half it's on. Turn off half of those breakers, repeat.
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Not a meme
lol
I'm a quality director and I did this the other day to identify the exact range of bad laminate in a number of film rolls!
It's not that the cops don't know how to search a video, they simply don't want to, because theft of property from you, a working-class nobody, is nothing to them.
It can also be both.
(Source: I have talked to cops before)
And also that - depending on the format of the video and software involved - doing a "binary search" might not be that simple
With my own NVR system, it takes great quality video and I can pull files of it, but the actual interface is pretty janky to say the least, and accessing stuff like the fisheye cameras only really works well within the vendor's app.
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