sniffnoy (
sniffnoy) wrote2025-08-12 11:47 pm
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NYC subway challenge
Inspired by seeing this old article on Hacker News, here's a challenge for you: In the (current) NYC subway system, find two stops A and B such that to get from A to B, you need to take 4 trains. (This isn't 1980 anymore; I'm pretty certain there aren't any pairs requiring 5 trains.) We can set out several difficulty levels:
1. Ultra-easy version: There just has to be some time of day / day of the week at which it works.
2. Easy version: It has to work on the normal subway schedule (meaning, weekday, not late-night, not rush hour, no peak-direction-only services, no other special stuff, the Times square / Bryant Park transfer is open).
3. Full version: It has to work no matter the time of day or day of the week.
We assume that the subways are in fact running as scheduled -- no reroutes or service reductions. You have to stay inside the subway system, inside the fare gates; out-of-system transfers are not allowed even if they're free, and if you want to turn around, you have to do it at a station where that's possible.
(Note: I'm not a subway expert, so I'm relying on the maps (including their legends and info) to be essentially accurate here. I'm aware that there's some more info that's not on the maps, but so far, I've yet to see anything relevant to the challenge, so I'm just going to hope there's truly nothing!)
Can you find how to do it?
( Answers in the cut )
1. Ultra-easy version: There just has to be some time of day / day of the week at which it works.
2. Easy version: It has to work on the normal subway schedule (meaning, weekday, not late-night, not rush hour, no peak-direction-only services, no other special stuff, the Times square / Bryant Park transfer is open).
3. Full version: It has to work no matter the time of day or day of the week.
We assume that the subways are in fact running as scheduled -- no reroutes or service reductions. You have to stay inside the subway system, inside the fare gates; out-of-system transfers are not allowed even if they're free, and if you want to turn around, you have to do it at a station where that's possible.
(Note: I'm not a subway expert, so I'm relying on the maps (including their legends and info) to be essentially accurate here. I'm aware that there's some more info that's not on the maps, but so far, I've yet to see anything relevant to the challenge, so I'm just going to hope there's truly nothing!)
Can you find how to do it?
( Answers in the cut )