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Jabatheblob1

Member

Joined: 2015-03-01

Posts: 856

Switches Riddle

So here's the riddle: You are one of 23 inmates that have been wrongfully accused of a murder. You all are in for a life sentence but you all know you're not guilty. The warden also knows this so offers for all 23 of you to play a game. The game goes like this, the warden will choose one person(of his choosing) each day to go into this room. This room has two switches(connected to nothing). While in this room, the inmate HAS to switch ONE switch, and only ONE switch. The starting positions of the switches is unknown to the inmates. The switch can either be on or off. The object of the game for the inmates is this, once they feel like every single person has gone through, they tell the warden and if they're right, they will go free... If they're wrong, they get killed.

Specifics:
Warden can choose anyone(meaning can choose the same person)
23 is not specific
This is not a play on words
(If you look up the answer it may be confusing... and i feel like i've come up with a better method)
The inmates have no communication with one another.
Before this game starts, the inmates have 1 hour to come up with a plan. After that, they will be sentenced back to their cells where they cannot talk to one another.
Find a method that's 100% positive(no probability)
No inmate can leave a trace of themselves in the room, or communicate in any other fashion other than the one switch they flip.
Switches are independent of one another.
Just one person has to tell the warden that all 23 people have gone through.

This is supposedly one of googles job interview questions.

I came up with a method in 15 minutes... Time yourself

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Abelysk

Guest

Re: Switches Riddle

Each member picks their nose. First inmate secretly wipes a small snot mark near the switch w/o the warden noticing. Second inmate marks the second snot mark. Switches don't matter. Once 23 snot marks are made, there is sure proof all inmates have went through.

If the same inmate goes twice, the inmate won't wipe his/her snot. This makes sure each member does it once until there are 23, ensuring all inmates have gone.

Jabatheblob1

Member

Joined: 2015-03-01

Posts: 856

Re: Switches Riddle

Each member picks their nose. First inmate secretly wipes a small snot mark near the switch w/o the warden noticing. Second inmate marks the second snot mark. Switches don't matter. Once 24 snot marks are made, there is sure proof all inmates have went through.

If the same inmate goes twice, the inmate won't wipe his/her snot. This makes sure each member does it once until there are 24, ensuring all inmates have gone.

Clever but no, i guess i should have specified(now edited), each inmate cannot leave a trace in the room other than the switch they have flipped.

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Zumza

Member

From: root

Joined: 2015-02-17

Posts: 4,656

Re: Switches Riddle

So this can last forever if warden wants so?

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Pingohits

Banned

From: aids lizard

Joined: 2015-02-15

Posts: 7,591

Re: Switches Riddle

(~7 minute solution)

during the 1 hour period when the inmates are conversing, they come up with this:

when the first person goes in, he needs to switch the switch on the LEFT, and ONLY on the LEFT

once he does that, if the left switch is facing UP, he waits 10 seconds while the inmates count. if he leaves at the 10 second mark, the inmates know the left switch is UP

if the left switch is facing DOWN, he waits 20 seconds while the inmates count. if he leaves at the 20 second mark, the inmates know the left switch is DOWN

after that, if 21 people (excluding the first person and the last person to tell the warden they have all done it) switch the left switch based on the details provided, then either:

if the switch was facing UP at start, after 21 people have switched it, it should be DOWN by the time the last person comes

if the switch was facing DOWN at start, after 21 people have switched it, it should be UP by the time the last person comes

after the last person tells the warden, they are all free men

EDIT: i just realized my mistake, but i'm leaving this here if anyone would want to expand on my idea or correct some faults

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Jabatheblob1

Member

Joined: 2015-03-01

Posts: 856

Re: Switches Riddle

So this can last forever if warden wants so?

That's not the point of the riddle, the point is to come up with a plan to determine with 100% certainty that all 23 inmates have gone through

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