273 comments

[ 3.3 ms ] story [ 258 ms ] thread
Good article, but what they failed to notice was that the bathtub already blocks both doors from opening.
Okay, how would tying the two doors together prevent the doors from opening if the doors opened inwards? It’s pretty obvious the doors would have to open outwards from the bathroom into each suite. So the bathtub’s size and position in any diagram is even more irrelevant, I’d suggest.
If one has always lived in a country where bathroom doors (or outdoors, for that matter) as a rule open inwards, maybe the idea of a door opening outwards is too distant to contemplate.
Well it is cheaper to change the direction of the door than it is to demolish and rebuild the hotel.
It's a poor drawing. They look like doors that open inward. Doors that open outward would be need to be set more deeply into the door frame.
A poor drawing and a worse excuse.

There's only one way this could work and how it's drawn has very little to do with it.

If they open inwards you replace the rope with a stick.
A stick can handle both inwards and both outwards, but if one is in and one is out then it's no good.
This sort of goes to something I learned as an auto mechanic. When you have a problem, describe the symptoms as objectively as possible. Don’t say, “I need my tires balanced.” Or you might get your tires balanced but the problem persists. Instead say, “I feel a vibration when driving on the highway at 60mph.” This forces the technician to diagnose the problem.

That’s an overly simplistic example but that’s the point. Tell your doctor what your symptoms are, without including statements that suggest a cause, or otherwise limit the scope of the issue.

That would be the right thing to do with a competent technician or indeed your doctor. However, here in India where I live, mechanics and computer technicians are for the most part essentially illiterate. They have absolutely no experience with the kind of analytical and critical problem solving skill you describe. Very often I am the expert in the room, and the only thing preventing me from doing the repair myself is the actual tooling (Plus I don't want to get my clothes dirty :-) ). So I do the do the diagnosis, and tell the mechanic what to do and they do it. Works well for all of us. :-)
That’s different then. You aren’t asking for someone to solve a problem for you. You are just paying them to perform a task. I’m referring to the issue addressed in the article about problem solving.
India has exceptionally skilled mechanics. I saw one resuscitating a worn axle by stick welding new metal onto it! (In the street)
Let me guess... Puegeot branded car?
Oops, forgot this funny add, yes too!

Full context for the other readers: The puegeot 206 have a known axle problem, leading to breaking up right after warranty expires: http://clubpeugeotuk.proboards.com/thread/3298/faulty-axle-o...

It can be solved by directly welding metal to the axes. Considering how popular the 206 is in India, I thouht the OP was also relating his personal experiences with having his Puegeot fixed

There are situations, however, where you have to know specifically what you want in order to get it. Using my personal experience with automobiles in Pakistan as an example, maybe 1 in 50 places that's capable of changing a tire also has a good quality balancing machine. If you've just purchased new tires and you know you're going to need all four wheels rebalanced, you have to intentionally seek out that rare place which has a modern digital tire balancing machine and knows how to use it.
I don't think it's simplistic at all. In fact I think it's core to product/requirement management if you're doing it well.

"Tell me what you want to do, not how you want it done."

Or in business with knowing that customers don’t want 1/4” drills, they want 1/4” holes.
Or they want to feel proud their home and show off to friends. Which means getting modern art on their wall, hence requiring a 1/4" hole, and hence the corresponding drill bit.
Let's briefly imagine the world where this thinking is taken to its logical conclusion.

So business thought, why bother with drilling, let's invent Modern Art Affixer, because that's what people really want to do.

(That we can vendor-lock them in this is just an added benefit.)

Then I need a screen mounted on a wall. I can't use Modern Art Affixer, and it's something not common for regular consumers to do, but fortunately there are some (appropriately more expensive) Screen Affixing services that mostly service other businesses.

Then I want to hang a DYI piece of equipment I made and I'm shit out of luck, because individuals doing DIY hardware are too small a market to justify dedicated products.

Coming back from this nightmare - the point is, what happened with the concept of technology empowering people? That is, giving them means to solve their own problems, instead of trying to sell a ready-made solution to arbitrarily specific problem? It's not that I mind very specific solutions - but without more general, empowering technology, we'd be limited to only solving specific problems that affect large enough amount of people to justify a business around it. I worry this already starts happening at the intersection of hardware and software (e.g. most IoT products can be seen as solving overly specific problems to vendor-lock people).

So big thanks to all businesses that keep assuming that what consumers really need are standard-sized drills.

That logical conclusion exercise basically how to suss out, and then create giant scale businesses.

When enough of these exercises in root cause analysis (which is a bad methodology) point to the same problem, and you can monopolize the solution for that singular problem, you have a massive win on your hands.

You have to either trust your mechanic or know enough to avoid getting flimflammed. An unscrupulous mechanic can cost you hundreds in superflous services easily.
This is an entire section of Zen and the Art of Motorcycle Maintenance.
You see this a lot in stackoverflow.com
What I see on SO is a lot of really annoying people refusing to answer simple questions because they believe, based on nothing, they know more about the question than the person who asked it.
Never ask them anything about Linux networking. They get so excited to gatekeep the information and tell you that you don't know enough to be safe doing whatever you're doing.
I've actually been super curious lately what happens if you route a PC's localhost to someone else's IP, but I have no clue how to ask on SO without baiting out the obvious "don't do this" and the generic "stuff won't work". Obviously, I could do it myself and explicitly see stuff not working, but I'd like to find out what actually happens under the hood and why things break; SO seems like an awful place for these kinds of "what if" questions and I don't know a better place to ask.
You're curious what happens if you add a route for 127/8 to somewhere other than the loopback interface? Or do you mean making it so that the hostname "localhost" resolves to something other than 127.0.0.1? Give it a try.
what I see on SO a lot is people assuming your question is an instance of the "XY problem" when it's not.
Also the case where for the original asker it really was was an XY instance, but now the top google result for "how do I fill a bathtub using a hosepipe?" goes to a Stack Overflow page full of people refusing to answer the question.
...which was then closed for being a duplicate of another question, even though they are different questions that superficially look similar
The thing is, 99 times out of 100 it really is an XY problem. If you're the 1 out of 100 then it sucks to be you; I guess the free advice is worth exactly what you paid for it.

I don't often make that accusation, but the last time I did that's exactly what it turned out to be. They were trying to dive deep into the internals of C++ to find out why their debugger was hanging, and what they were asking for just didn't have an answer. They finally found that they were doing something that led to undefined behavior, and if they had asked about that instead the question would have been answered immediately.

I have ~7k reputation there, that should be a pretty strong signal, but apparently it's not.
The person asking the question above has a 5k reputation. Mine is over 100k so I've seen quite a bit.
When asking "unpopular" questions on SO I usually include a disclaimer along the lines that I want to know the answer for education purposes and any answer that is not specifically addressing the question at hand will get downvoted and never accepted. This works to some extent.

In the end, I stopped asking questions on SO because dealing with this kind of behaviour was too tiresome. I'm glad to see I'm not the only one who thinks like that

It heavily depends on the tag.

Some tags have friendly communities that will give a dozen of pointers in the comments.

I see mostly homework problems on SO.
I see mostly lively threads that are closed by moderators as 'offtopic'.
First step of any technical support case, or just troubleshooting anything is "Define the problem" and that includes when it happens, the circumstances, the circumstances when it doesn't happen, and etc.

One of my first real jobs I quickly became the favorite of some folks on the engineering team. The thing was I was not experienced, I didn't know much, but I followed a simple formula to write up problems, and they liked that. I often missed some basic steps and didn't have experience, but for whatever reason they liked how I gave them information. Also when they asked a question I was very clear and honest with "I don't know" and "I'll find out".

Other smarter techs would make assumptions based on their experience, fiddle with this and then, and then present to engineering this rambling tale that was all about what they tired to fix the problem and didn't fix it.... all while missing what the problem was in the first place, when it happened, and so on.

Not only tech support but also sales.

When I attend trade shows, I often have potential customers come and ask if we sell a particular type of technology. I’ve discovered that really what they are doing is asking if we sell the think they they _think_ is the solution to what they _think_ is the problem. It’s my job to figure out what their problem _actually_ is and then figure out if we have something that can solve _that_ problem.

One has to be quite diplomatic in these situations. They certainly know more about their domain, but I know more about technologies to solve their problem. So I need to pry out more information without sounding like I think I know more about their job than they do.

I like that part of the job.

Nice; the generalized version of "if I'd asked my customers what they wanted, they would have said a faster horse".
On the other hand, the job often turns out to be knowing the set of problems for which you're selling a solution (which is quite large for some companies e.g. Oracle) and then convincing the potential customer that this is the real problem that they have.
Interesting; this is sort of the flip side of one of the slides here: https://news.ycombinator.com/item?id=17532360 "Cognitive Distortions of People Who Get Stuff Done". One of the items is "Correct Overgeneralization", which seems to be basically what you describe in the last paragraph. Making assumptions based on experience, but being mostly right. Surely there's some balance to be struck: there's value in experience -- it can help you move faster -- but you have to be able to recognize and question your assumptions if need be. Sounds like your "smarter techs" were missing that step. They didn't circle back after their shortcuts failed them.
Absolutely there is value in experience! I don't want to discount that at all. I was way more productive longer-term for sure. And those techs weren't bad by any means.

The critical points in my example were failing to properly define the problem, and to some extent failure to communicate when engaging engineering created more work, delay, and frustration.

Yes. Don't assume, describe the context and explain the reason for your request.
This is true when giving feedback on games too when playtesting! As a designer, I love it when players say "I was frustrated when facing X, and had a lot of fun when doing Y interaction", rather than things along the lines of "I think X is too strong and needs to be balanced by doing W, but I think you should keep Y exactly as it is because it's just right."

Goes for both video and tabletop games. In general it's good to be able to articulate your "root issues" and work your analysis of the experience from there (if that's your responsibility, otherwise leave it to the people whose responsibility it is, the root issues are the only information they need).

Yep, this is generalized as the "standard litany" for bugs reports/request for assistance:

https://jdebp.eu/FGA/problem-report-standard-litany.html

and if you don't provide that you risk to slip on a chocolate covered banana (or XY problem):

https://jdebp.eu/FGA/put-down-the-chocolate-covered-banana.h...

This often got me into trouble on IRC. Sure there might be a more elegant way to do it, but I'm learning here!

Curiously I also regularly got into trouble for what I trying to do, not just the how.

For IRC, you need to go through the (only seemingly dated), a bit lengthy, but really exhaustive:

How to ask questions the smart way ... (by Eric Steven Raymond)

http://www.catb.org/~esr/faqs/smart-questions.html

Sometimes a subtle difference in the wording of the question may make the difference from receiving one or more helpful/useful replies and getting some snarky reply.

"subtle difference"

To me, that's hazing. There absolutely are bad questions, but the things that make them bad are rarely subtle.

Good luck with that when contacting Comcast or AT&T.
The bathroom in my house is like this. This solution would make me happy, but perhaps is too weird to be worth explaining to visitors.
I'd imagine visitors would marvel at the succinctness of the design, and it'd be a talking point!
Unless they're HNers, in which case they'd take great delight in demonstrating their superior intelligence by explaining why your locking system is ineffective due to various hypothetical scenarios.
Or attach the lock mechanism to the toilet so when a door is opened it flushes
I’d find it rather difficult to use a bathroom that was divided in half by a leather thong.
The strap could be diverted around a pully so the room is still usable
Why, because of the string thru the room? It can be placed along either side of the wall.
I think just because thong is a funny word that means different things in different places
(comment deleted)
The word means a (leather) strap - which is why thong underwear and thong sandals are called "thongs" that's what they're made of ... like rubbers being called rubbers (kinda, note a rubber in en-gb is both an eraser and a prophylactic).
I have trouble seeing how it could be placed along the wall while maintaining the necessary tension.
Through rings bolted to the wall.
Good (and in retrospect, obvious) point!
Yeah, I misunderstood things worse: I thought doors opened inwards, and that the ropes were somehow rigid (basically rods).
I suspect the door opening was already close to a wall. Just make sure the hinge is on the side farthest away from the wall.
(comment deleted)
I don’t think the illustration is accurate. You can imagine a room where the doors are right next to each other.
I visited some dorm rooms in Croatia once, and they had a nice solution to this problem. Both doors opened inward, with the non-hinge side of the doors sitting very close to one of the walls with no doors. Instead of a conventional lock, a narrow piece of wood ran the length of this no-door wall that could be rotated to block both doors simultaneously.

This is like the solution in the article, except deals with the "opens-inwards" case instead of the "open-outwards" case, and is less fumble-y than having to attach a rope to both doors.

Do you have a picture or a diagram of this? I'm finding it hard to visualize.
|\ /| imagine those being the doors slightly open into the room.

Now here it is with the doors shut and the wood beam between them. ||__||

Can’t open either inward until the beam moves.

The thing in the middle is a stick attached to the wall on a hinge.

View from above - open:

  |\__.__/|
View from above - closed:

  ||_____||
The whole thing at “face level” with the pushing beams sliding in guiding loops.
I just can't believe I understood the whole concept so easily by the creative use of ASCII characters!!

Thanks.

But if the beam somehow fell/rotated in place while no one was in there with the doors closed, you'd be locked out without a non-destructive way to unlock it.
The same issue applies if the person inside is unconscious or otherwise unable to help.
You make the beam weak - strong enough to avoid accidental breakage, weak enough that a solid shoulder will break it. You also make the rotation cammed in such a way that gravity holds the beam failed open.
I've seen a similar solution in the swimming pool changing cubicles at a Center Parcs in the UK. The cubicles have two inwards opening doors opposite one another. Once inside, you close both doors and fold down a bench which blocks the doors shut and gives you somewhere to sit. Very clever solution.
Except if there is a fire and you realise it's stuck. A normal lock can be kicked in if not opened with master key, but that contraption sounds hard to break in to.
I feel like a fire at a swimming pool might be more rare than a fire elsewhere, just by virtue of being surrounded by water (pool, showers, etc). Maybe I'm wrong.
True. You might get smoke from somewhere else in the building though.
I'm imagining that doors on "swimming pool changing cubicles" are flimsy enough to kick outwards.
No idea about this specific example, but if it is anything like normal bathroom locks, I'd expect that you'd be able to rotate the bench back upwards with some sort of key/screwdriver/lever from the outside.

I'd worry about someone being ill while sat/leaning-on/collapsed on the bench though meaning you cant rotate it. I guess this is an issue for any door where a body could block it being opened? At the least in a changing room cubicle these are usually open at the top so someone could climb over in an emergency.

There are large gaps above and below, plus the hinges are plastic and the walls are plastic covered chipboard (or something similar.

The bench lifting is part of the system - you can't leave rubbish or water on the bench.

You could solve a safety access issue by having the bench corner removed and replaced with a breakable component; but I'd speculate the materials are such the hinges already serve that purpose and changing the corners would lead to a lot of accidental breakage.

There is better solution used everywhere else.

The bench stays in place. Both locks are linked by a bar, that can be conveniently hidden under the bench. When rotating any lock, they both rotate together.

If you have to fold the whole bench to get out you are less likely to accidentally leave something behind. But I guess the real reason for this design is probably that folding the bench saves some space.
Wow, thank you. I have been struggling forming the mental picture in my head of how the leather rope could work... I didn't even think that the doors would be opening outwards from the bathroom.

Upvoted :)

You could leave your door open and still lock out the other in this case.
I think assuming malice the problem becomes much harder.
I wasn't thinking malice actually. You might just want to use the bathroom with your own door open and not think anything of it.
In that situation the open outwards/rope solution is indeed more save.

In your case you could design it such that you can’t close the door after use without unblocking the other one. Typically people would like to close the door to the bathroom after usage.

As used in pretty much every swimming pool I've ever been to.
No need for a strap, Bluetooth linked locks that are automated so when one opens the other does to. Or put the lock on the wall rather than on the door and have a mechanical device running up and through the roof to the other door, configured such that the two door locks are restricted similar to the automation.
Battery dies every so often and guests complain. Also, Bluetooth. It's often unreliable.
This hotel was built over 100 years ago and was destroyed in a fire in the 1960s. The article isn't about how to actually solve the problem of locking shared bathroom doors... it's about sharing insights into how designers were better able to solve a problem by focusing on the objective rather than focusing on the implementation.
But why the need for Bluetooth, when you have a strap?
I'd know what I'd bet on to actually work.
> You could, of course, tear down and rebuild the entire hotel, at great expense, so that each room has its own bathroom—a solution that might sound ridiculous, but isn’t so far removed from how similar design problems are addressed every day.

The 'similar design problems' link in this sentence points to an article about how the video game Destiny was delayed due to a story re-write. What on earth?

>where bathrooms share a bathroom

Is this a typo?

In the Hotel Louis IV even the bathrooms have bathrooms (but the guests still have to share)
I think it should read "where bedrooms share a bathroom".
Another way would be to make the the lock a large rotating latch that was connected mechanically to a similar latch on the other side.

While this would be more complex, it wouldn't get in the way as much.

Another possible solution:

Each side has two locks: one that is locked when the key is missing, and one that is locked when the key is present. To give yourself privacy, you must also lock yourself in. To exit the room, you must first unlock the other door and use the key to unlock your own door.

That would violate fire codes almost everywhere.
It’s also asymmetrical. The occupant of the locked-when-key-is-present room would have no incentive to return the key and to unlock the opposite room door.
(comment deleted)
It’s not really assymetrical: both sides have one key and two locks. But you’re right that it won’t work.
Nope, ignore me. This protocol has a fatal vulnerability: either user can just remove the other side’s key, and put it on the windowsill.
You can use sensors to figure out if someone is inside these days. Tech is cool.
The sensors have a lot more failure cases, though, and it can be hard to tell whether they're working properly.
Reminds me of light sensors in bathrooms. Often you have to wave your arms to let the sensor know you’re still inside.
Yeah, that's what I was thinking of too. Don't relax in the tub too long or the doors will unlock!
That could be a feature, for someone waiting to use the facilities...
This entire treatise presumes not using one switch, two locks. Cars seem to have no trouble with this.
Electronic locks was not a thing in 1900. Old cars with manual locks did indeed have the cases where the driver reaches over and locks the passenger door, when the passenger forgets to lock it themselves. And users of old cars will remember the "open front door, reach inside and unlock back door" maneuver.
Central locking: if you're in the centre of the car yu can lock all the doors.
When I was a young child I tied the pantry light's pull chain to string and tied the string to the door handle, just taut enough that it would enable the light when the door was opened.

Regretfully to shut the light off, I needed to first close the door, re-open the door and then finally close it.

Crafty. I like it. It's funny the little (and not-so-little) things we put up with, just so we can bask in the joy of our own creations.
In other words, the bathroom is a "critical section" and instead of focusing on locks on each door, it's been replaced with one big "lock" that locks them all at once.
It makes the transaction atomic.
You can do that with two locks too, but one is simpler.

Also, there is a failure mode here. Can you think of it?

Death of the person in the bathroom? Damage to the hooks causing a jam or releasing the lock entirely? Simply not engaging the lock at all? Someone walking off with the thong and using it creatively elsewhere in their hotel? A few failure scenarios. Nothing's perfect!
Death or incapacitation of the person in the bathroom is what I had in mind.

Yes, there's also the leather strap or hook (or doorknobs, ..) breaking. I hadn't considered that, oy.

I can't see what failure mode that the single lock has that isn't the same in the 2 locks version.
I often share the bathroom with my wife, and we don’t always enter at the same time. I.e. sometimes you don’t want to lock your own door.
Just thinking about this for a minute or so, I don't think there's a way of allowing /only/ one door to remain open-able ('unlocked') that solves the problem. Either both must lock/unlock in the same action or there must only be one door to the restroom (that is, duplicate the resource).
If the two people are accessing the bathroom from the same side, locks are not a problem. Three or more people sharing the bathroom is a different problem.
A designed degradation, also common in software. For instance, the low battery mode in iOS is a designed degradation around the fact that is close to impossible to improve the capacity of a lithium battery (the soloution would be a completely new kind battery) so they allow people to disable non-critical features to get a slower battery drain.

“Unlike common designs, excellent designs can circumvent the existence of “unhappy” conditions as well as the influence of other low-performance designs. Many times this requires the new design to lower its own performance and although this is not ideal, this is usually a trade-off that can help to maximize the existing conditions.”: https://uxdesign.cc/designed-degradations-ux-patterns-for-ho...

In what way is the design of the room a degradation? As I understand it, the hooks work as well as (if not better than) the locks you'd otherwise have.
The degradation is the string that keeps both doors shut. It degrades the experience of the bathroom because it limits mobility inside of it but this degradation was designed to circumvent a larger deficiency of the design (shared bathrooms).
The hooks could double up as towel racks. And also, if the doors are near to the edge of the wall, the hooks will be near the wall too, and so not really take up space.

And it's not like you'll be dancing in the bathroom, so it taking up some room that otherwise won't really be used isn't as big a problem as privacy.

In product management this is often described as problem space vs solution space.

One of my biggest lessons in “managing up”: agree on the problem, and take any suggestions for a solution seriously. Then work to make the solution you present as good or better.

> often described as problem space vs solution space .... agree on the problem

The hard part being agreeing on the problem!

Sometimes, management sees the "solution", and present it as a problem that engineers then must solve. For example, competitor has brand new feature, and management asks said feature to be implemented (presumably, keeping up with the jones style). But the actual problem isn't lack of said feature, but that customers are not buying, and the only reason that's presented is a lack of said feature.

Wouldn’t this make it easy to get into the adjacent guest room?
They could still have locks on the doors, but the locks would be to keep people out of the hotel rooms, not out of the bathroom.
I believe the parent is suggesting that the two rooms adjoining the bathroom would be mutually accessible when they shouldn't be.
(comment deleted)
Yes, so you have a lock on the door that you can only manipulate from your room. Unlock it when you need to use the bathroom, lock it otherwise.
This of course doesn't allow you to lock the bathroom when you're in it from other people also in your hotel room. Although this is certainly much less of a concern.
so then you need to remember to bring your hotel key into the bathroom.
Why? It’s not a key, just a lock you open/close from inside your bedroom into the shared bathroom. Once you are in, you can just walk back into your room unless someone in your room on purpose locks you in.
There's a lock on the bedroom side of the door.
(comment deleted)
Ah, but there is one failure mode... Can you find it?
Guess not. The failure mode is: the person in the bathroom becomes incapacitated or dies.
The bathroom connects two rooms where you don't know or trust the other room.

Without a lock you have no way to prevent them coming into your room when you are not there.

Still that is some great out of the box thinking.

That thought occurred to me, too, but I realized that you could add locks that could only be locked from the bedroom sides.
Yes, but then the problem becomes possibly being locked out of your own bedroom, stuck in the shared bathroom!
How? If someone from your room on purpose locks you in the shared bathroom? That doesn’t sound like a likely scenario
I lived in on-campus student housing that had bathrooms like this (the locks on both sides of both doors version.) My friend was in the bathroom during a commercial break of X-Files and I locked him in there. Ha ha. So he knocked on my neighbour's door and got out that way, but he still needed to get back into my room from the public hallway. I was watching him through the peep hole in my door, and to taunt him I opened the door and quickly closed it again. The two problems with that were that the peep hole made it look like he was further away than he was and the door had a hydraulic arm on it and didn't close as quickly as I expected. Anyway, I put ice on my forehead for the rest of the episode and then went to the hospital for three stitches.

I'd say that the likeliness really depends on whose bathroom it is. ;)

May not be likely but does seem like this would be in violation of fire codes. (Possible lack of free egress)
That could always happen regardless of the locking mechanism.
The solution still allows you to lock your own room from bathroom entry (though it isn’t this way, weirdly, at the hotel in question).
What if the high humidity of the bathroom causes the leather strap to break at an inopportune time? What happens if the strap gets misplaced or stolen? This is not a good idea.
> What if the high humidity of the bathroom causes the leather strap to break at an inopportune time?

I doubt that would happen, but use something other than leather?

> What happens if the strap gets misplaced or stolen?

Replace it?

(comment deleted)
A surprising number of these comments are trying to find problems with the solution.

I've noticed a tendency for hackers to assume that practical solutions to real world problems are theoretical, and then try to pick holes in them, forgetting that if the solution is already implemented and in place, then it probably works just fine.

Why settle with "just fine"?
Opportunity cost. Time spent trying to come up with a better solution to something that doesn't need a better solution, is time that isn't being spent doing something more valuable.

OTOH, one could argue that pursuing a seemingly trivial improvement to an existing solution could - by serendipity - lead to a breakthrough that actually does solve other problems as well. But I'd guess that, on balance, there's a greater payoff for spending time on something besides incremental tweaks to existing solutions. But that's just a guess...

But that’s a big part of designing anything: Trying to find a solution’s faults to then be able to implement a better one or at least be aware of the faults and work around them. I don’t see anything wrong with that.
To echo you, that's also one of the things you painfully learn when working with real software systems: there will always be failure cases you didn't think of. Better to catch as many as possible early. Just because it's working now doesn't mean it will keep working tomorrow.
> find problems with the solution

You would be surprised to know how many nobel prize winners do that.

Really? How many?
As everyone else is trying to re-solve this problem in a better way... Here's my 2p's worth:

Employ a monkey to lock/unlock both doors for you. Use something like a banana for lock and an orange for unlock, keep baskets of both fruits in the bathroom. To stock the baskets get the maids to do it when they change towels.

I would pay good money to stay at a hotel that utilises monkey-lock-fruit-bowl arrangements
One ticket for the lockpicking monkey circus please
Has nobody ever been swimming?
I have never seen this situation at a swimming pool, and I have no idea why it would be necessary at all? Just have a cubicle with a shower curtain, or an ordinary change room.
All swimming pools in the UK have cubicles with two doors - one that leads to the pool and one that leads to the exit. There isn't any way around the cubicles.

It's to prevent people casually walking into the pool in shoes and making it dirty.

They use a single piece bar that locks both doors simultaneously.

No one has mentioned this yet: remove the two private doors and install a single door in the common hallway.

Yes you lose some convenience by having to be clothed while entering and exiting the bathroom. But at least you guarantee the door is always unlocked when not in use.

(comment deleted)
That's only possible if the bathroom is next to the hallway, otherwise they have to tear down the building.
I get what the author is getting at. But this particular example doesn't really help with the conclusion. The solution is still about locks, just that the 2 locks are now linked together.
There are no locks in doors at all. There is a single mechanism physically connecting the doors together, so that neither can be opened, and that can only be engaged and disengaged from the inside.
How is that mechanism not, itself, a lock? It's an unusual (and well suited) kind of lock, sure, but still a lock.
Try pointing to the part that is the key that unlocks it, and you will see. (-:

Yes, strictly speaking the headlined article is likely talking about door bolts not locks.

There are plenty of locks that do not use keys, e.g. a keyless deadbolt.
No. The key that unlocks a "keyless" deadbolt is the code that one types in.
That type exists, yes. There is also the variety that is simply impossible to unlock from one side.