• Log InLog In
  • Register
Liquid`
Team Liquid Liquipedia
EDT 19:02
CEST 01:02
KST 08:02
  • Home
  • Forum
  • Calendar
  • Streams
  • Liquipedia
  • Features
  • Store
  • EPT
  • TL+
  • StarCraft 2
  • Brood War
  • Smash
  • Heroes
  • Counter-Strike
  • Overwatch
  • Liquibet
  • Fantasy StarCraft
  • TLPD
  • StarCraft 2
  • Brood War
  • Blogs
Forum Sidebar
Events/Features
News
Featured News
[ASL22] Finals Preview: Sweet Victory!9[ASL22] Ro4 Preview: Mirror Mirror6[ASL22] Ro8 Preview: Within Reach5[ASL22] Ro8 Preview: In A Tizzy11[ASL22] Ro16 Preview: Holy Diver5
Community News
Evil Geniuses - shutting down13ISSL (IntoTheTV x SOOP SC2 League): Premier5Weekly Cups (October 12-18): 5.0.17 era begins1[$1250] International ShieldBattery League55Weekly Cups (October 5-11): Farewell to 5.0.167
StarCraft 2
General
REPORT: StarCraft 2: Remastered In Development Evil Geniuses - shutting down How do you feel about the mass reverts in the 5.0.17 PTR? No more SC2 streamers on team liquid? Daily SC2 Player Grid - feedback wanted
Tourneys
ScienceCraft (October 24-25) - Live Event RSL goes to London! 2026 Offline Finals Nov 21-22 ISSL (IntoTheTV x SOOP SC2 League): Premier Sparkling Tuna Cup - Weekly Open Tournament WORTEX Challenger Series — Open SC2 LAN in Budapes
Strategy
[H] ZvP Mid-Late Game: Stalkers Collossi HT
Custom Maps
[G] How to playtest arcade maps [A] Nemrods 1/4 players [M] (2) Sweltering Sands [M] (2) Frigid Storage
External Content
Mutation # 548 Shining Bright The PondCast: SC2 News & Results Mutation # 547 Temple Of Terror Mutation # 546 Catch the Train
Brood War
General
Starcraft player cRuZa Passed away. Young Players Tournament Announced by SOOP SCHNAIL now supports Remastered BGH Auto Balance -> http://bghmmr.eu/ BW General Discussion
Tourneys
[ASL22] Grand Finals [Megathread] Daily Proleagues KCM Race Survival 2026 Season 4 [$1250] International ShieldBattery League
Strategy
50,000-Word Terran Builds Memo 2026-10-22 Cliff Jump Revisited (1 in a 1000 strategy) Simple Questions, Simple Answers
Other Games
General Games
Stormgate/Frost Giant Megathread Armies of Exigo - YesYes? Nintendo Switch Thread General RTS Discussion Thread Dawn of War IV
Dota 2
Dota 2 Champions League Season 3 Begins April 25!
League of Legends
[TL LoL EUW IHs] Teemo shall perish
Heroes of the Storm
Heroes of the Storm 2.0
Hearthstone
Deck construction bug
TL Mafia
TL Mafia Community Thread
Community
General
US Politics Mega-thread Things Aren’t Peaceful in Palestine Artificial Intelligence Thread Canadian Politics Mega-thread Russo-Ukrainian War Thread
Fan Clubs
Serral Fan Club
Media & Entertainment
[Manga] One Piece Anime Discussion Thread Movie Discussion!
Sports
Football (Soccer) Thread TeamLiquid Health and Fitness Initiative For 2023 MLB/Baseball 2023
World Cup 2022
Tech Support
Computer Build, Upgrade & Buying Resource Thread
TL Community
Recent Gifted Posts
Blogs
How Much Genes Contribute to…
TrAiDoS
ShieldBattery on Mac
Kraekkling
[ASL22] Ro4 Day1 Ticket Giv…
bITt.mAN
38 yo Retired SWE loo…
PurE)Rabbit-SF
Can Bots Beat Pros?? Starcr…
namkraft
Customize Sidebar...

Website Feedback

Closed Threads



Active: 10431 users

New Math Puzzle

Blogs > Slithe
Post a Reply
1 2 Next All
Slithe
Profile Blog Joined February 2007
United States985 Posts
March 12 2008 08:03 GMT
#1
The prisoners are back for more puzzles! And this time there's a light bulb in the mix.

There are 100 prisoners, each in their own isolated rooms. There's another special room with a light bulb and a switch, and nothing else. The light bulb is initially off.

One at a time, a prisoner is chosen at random to go into the special room. The prisoner can choose to either flip the switch or not. The prisoner will then leave the room and a guard will ask him whether he he thinks all 100 prisoners have been in the room at least once. The prisoner can either answer "yes" or "don't know".

If he answers yes and he's correct, all the prisoners go free.
If he answers yes and he's wrong, all the prisoners are killed.
If he answers don't know, then the prisoner goes back to his room and the process continues.

Before the prisoners are put in their rooms, they get to decide beforehand on a strategy. What strategy should the prisoners use to assure the survival of the prisoners?

Key Point: The prisoners can go into the room multiple times, and the order is random. For example, prisoner 1 could potentially go into the room 10 times before prisoner 5 goes in even once.

EmeraldSparks
Profile Blog Joined January 2008
United States1451 Posts
March 12 2008 08:12 GMT
#2
+ Show Spoiler +
If it is your first time in the room, flip the switch. Wait until you have been brought in for the hundred thousanth time and all you have seen is an off light-bulb. On the hundred thousanth time, declare that all the prisoners have been there. The laws of chance say that it's just a little bit unlikely that somebody would be chosen a hundred thousand times before somebody else was chose once.

Better make that a million.
But why?
leejas
Profile Blog Joined August 2007
United States440 Posts
March 12 2008 08:23 GMT
#3
Thats laws of odds though, still a small chance you could get shot in the face.
leejas
Profile Blog Joined August 2007
United States440 Posts
Last Edited: 2008-03-12 08:43:22
March 12 2008 08:32 GMT
#4
+ Show Spoiler +
One solution I managed to come up with...it's safe too.

Before 100 days, leave the switch off if it's your first time in. Then if someone comes in two times, they turn it on. The next person to come in flicks the switch off. He now knows that the number of days before him is the number of unique people that have been in the room. After that, you use a new rule. Leave the light on if you've been in the room. Turn it off if it's your first time. Now, whoever has been in the room two times knows that he has the remainder to count. So he counts off each time he goes in the room if the light is off, until it's been 100 times.

GG? Takes too long I think. Should be another solution.


Cascade
Profile Blog Joined March 2006
Australia5405 Posts
Last Edited: 2008-03-12 08:43:45
March 12 2008 08:37 GMT
#5
Isn't this very similar to the other prisoner problem with the thingy they turned up and down, but then it was more complicated, because they had that stupid king that could mess with them?

The same solution would work, right?

I dont know what to say about the recuring apearance of prisoners and light bulbs either. :o

edit: leejas:

+ Show Spoiler +
So the "yes" condition would be that you had seen the light being switched 100 times? But if two prisoners is in the room between two of your visits, you will not see their switches, and you will never get to 100. You want a solution that always works. And I dont think "but this will take a lot of time" is a flaw. These prisoners in general have A LOT of time on their hands...
NarutO
Profile Blog Joined December 2006
Germany18839 Posts
Last Edited: 2008-03-12 08:46:08
March 12 2008 08:43 GMT
#6
On March 12 2008 17:12 EmeraldSparks wrote:
+ Show Spoiler +
If it is your first time in the room, flip the switch. Wait until you have been brought in for the hundred thousanth time and all you have seen is an off light-bulb. On the hundred thousanth time, declare that all the prisoners have been there. The laws of chance say that it's just a little bit unlikely that somebody would be chosen a hundred thousand times before somebody else was chose once.

Better make that a million.



+ Show Spoiler +


The riddle is not correct. The prisoners may communicate and discuss a plan beforehand. Your solution is not possible, because you will just have 1 prisoner / day which means you would have to wait 100000 days with your solution or even 1000000 which is equal to 273 years (100000) or 2739 years (1000000).

Given the fact that they may discuss beforehand, one person is chosen as the counter. If the light switch is on, no prisoner will touch it. If it is off, and a prisoner who has never flicked the switch enters, then he flicks the switch on. It stays like that until the counter returns. The counter never flicks it up, only flicks it down. Once he notices that it's been flicked up 99 times, he says that 100 prisoners have visited, and they go free.

This is the solution.. ;o

NOTE: It could still take years.. or never happen if its really random

CommentatorPolt | MMA | Jjakji | BoxeR | NaDa | MVP | MKP ... truly inspiring.
leejas
Profile Blog Joined August 2007
United States440 Posts
March 12 2008 08:43 GMT
#7
Check my update.
LTT
Profile Blog Joined March 2003
Shakuras1095 Posts
Last Edited: 2008-03-12 08:52:27
March 12 2008 08:49 GMT
#8
The problem, lee, is that you don't know that this is going to be once a day. Slithe didn't specify an interval. You can only break it into two phases like that with either a set interval between iterations or if every prisoner knows what iteration they are on.

Edit: Grammar.
leejas
Profile Blog Joined August 2007
United States440 Posts
Last Edited: 2008-03-12 09:00:33
March 12 2008 08:57 GMT
#9
Sorry, it's 5am here and I'm studying for an exam :D.

Anyway, you're gonna have to do it the other way then.

Leave the light on all the time. If someone new comes in, they turn it off. If you go in, the light is off, someone new was there, thus, it's one note. After that, you have to count off how many times you've been in the room to 100. After that, everyone's been there.
Zalfor
Profile Blog Joined October 2005
United States1035 Posts
March 12 2008 08:58 GMT
#10
naruto is so correct.
555, kthxbai
spammerA
Profile Joined July 2006
China355 Posts
March 12 2008 09:28 GMT
#11
On March 12 2008 17:43 G.s)NarutO wrote:
Show nested quote +
On March 12 2008 17:12 EmeraldSparks wrote:
+ Show Spoiler +
If it is your first time in the room, flip the switch. Wait until you have been brought in for the hundred thousanth time and all you have seen is an off light-bulb. On the hundred thousanth time, declare that all the prisoners have been there. The laws of chance say that it's just a little bit unlikely that somebody would be chosen a hundred thousand times before somebody else was chose once.

Better make that a million.



+ Show Spoiler +


The riddle is not correct. The prisoners may communicate and discuss a plan beforehand. Your solution is not possible, because you will just have 1 prisoner / day which means you would have to wait 100000 days with your solution or even 1000000 which is equal to 273 years (100000) or 2739 years (1000000).

Given the fact that they may discuss beforehand, one person is chosen as the counter. If the light switch is on, no prisoner will touch it. If it is off, and a prisoner who has never flicked the switch enters, then he flicks the switch on. It stays like that until the counter returns. The counter never flicks it up, only flicks it down. Once he notices that it's been flicked up 99 times, he says that 100 prisoners have visited, and they go free.

This is the solution.. ;o

NOTE: It could still take years.. or never happen if its really random



nice one
useLess
Profile Blog Joined January 2004
United States4781 Posts
March 12 2008 09:40 GMT
#12
Man, saw this on the william wu riddle website years ago
Moonlight Shadow
betaben
Profile Blog Joined September 2007
681 Posts
March 12 2008 09:44 GMT
#13
my favourite puzzle:

http://epicycle.org/2006/04/hardest-logic-puzzle_25.html
stenole
Profile Blog Joined April 2004
Norway869 Posts
March 12 2008 11:00 GMT
#14
It feels like it's the same riddle all the time.

Prisoners are presented with a a set of rules where ultimately their behavior leads to death or freedom. They get to discuss a strategy to beat the system for their freedom. Thereafter, they are instructed not to communicate directly. The system often has a certain set of artifacts such as light switches, light bulbs and rooms which they have to interact with. Any other interaction is not allowed. Strangest of all, the system they have to beat is always beatable. But in such a situation, can the guards be trusted? Why would they make a game like this that could guarantee the prisoners freedom? Can the rules be trusted? Can the prisoners be trusted to follow the strategy? Can the prisoners be trusted not to cheat? These are all reasons why people should not be used in riddle, unless the solution is about thinking outside the box.
sundance
Profile Blog Joined May 2004
Slovakia3201 Posts
March 12 2008 13:29 GMT
#15
On March 12 2008 20:00 stenole wrote:
It feels like it's the same riddle all the time.

Prisoners are presented with a a set of rules where ultimately their behavior leads to death or freedom. They get to discuss a strategy to beat the system for their freedom. Thereafter, they are instructed not to communicate directly. The system often has a certain set of artifacts such as light switches, light bulbs and rooms which they have to interact with. Any other interaction is not allowed. Strangest of all, the system they have to beat is always beatable. But in such a situation, can the guards be trusted? Why would they make a game like this that could guarantee the prisoners freedom? Can the rules be trusted? Can the prisoners be trusted to follow the strategy? Can the prisoners be trusted not to cheat? These are all reasons why people should not be used in riddle, unless the solution is about thinking outside the box.


It's just a riddle not real life situation ffs.
Nick Cave & the Bad Seeds
drift0ut
Profile Blog Joined June 2004
United Kingdom691 Posts
Last Edited: 2008-03-12 14:34:19
March 12 2008 14:33 GMT
#16
I've not read all the posts but this does it:

+ Show Spoiler +

Pick one man, DAVE,

if you are not DAVE:
if it's your first time in the room: flick the on if it's off, leave it on if it's on
if you've been there before: leave it

if you're DAVE:
if it's on count:=count +1 and switch it off,
if it's off leave it
when you count to 100 (or 99 really) you are done


edit: G.s)NarutO got it first, gg
Slithe
Profile Blog Joined February 2007
United States985 Posts
March 12 2008 16:48 GMT
#17
Congratulations to Naruto, I think he got it first.

@betaben: That puzzle is a pretty good one. I've heard a very similar version with the key difference that there is no time limit, and the question is "How many days does it take for the diseased ones to kill themselves off". I dunno if I would call it "The hardest logic puzzle" though.
gwho
Profile Blog Joined January 2008
United States632 Posts
March 12 2008 17:52 GMT
#18
the strategy is this: if you flipped the switch and the gaurd asks you if you flipped it, say yes. if + Show Spoiler +
you didn't flip it say don't know -_- how easy xp
gwho
Profile Blog Joined January 2008
United States632 Posts
March 12 2008 17:52 GMT
#19
+ Show Spoiler +
the strategy is this: if you flipped the switch and the gaurd asks you if you flipped it, say yes. if you didn't flip it, don't say that you flipped the switch! -_- easy xp
gwho
Profile Blog Joined January 2008
United States632 Posts
March 12 2008 17:57 GMT
#20
On March 12 2008 20:00 stenole wrote:
It feels like it's the same riddle all the time.

Prisoners are presented with a a set of rules where ultimately their behavior leads to death or freedom. They get to discuss a strategy to beat the system for their freedom. Thereafter, they are instructed not to communicate directly. The system often has a certain set of artifacts such as light switches, light bulbs and rooms which they have to interact with. Any other interaction is not allowed. Strangest of all, the system they have to beat is always beatable. But in such a situation, can the guards be trusted? Why would they make a game like this that could guarantee the prisoners freedom? Can the rules be trusted? Can the prisoners be trusted to follow the strategy? Can the prisoners be trusted not to cheat? These are all reasons why people should not be used in riddle, unless the solution is about thinking outside the box.



idiot, it's a math riddle. the setup is similarbecause you don't want to say "x y to the squre root of 2 lbahlbahlbha, solve it." assume! assume the rules acn be trusted assume th eprisoners can follow the same strategy assume they can be trusted not to cheat geez. it's not thinking about outside the box. even my though answers always are, im just kidding. u couldn't even figure out the question itself. -_-
1 2 Next All
Please log in or register to reply.
Live Events Refresh
Next event in 9h 58m
[ Submit Event ]
Live Streams
Refresh
StarCraft 2
NeuroSwarm 206
Nathanias 99
SpeCial 87
ViBE79
StarCraft: Brood War
ProTech180
Dota 2
syndereN761
League of Legends
Doublelift4624
JimRising 785
Counter-Strike
Fnx 1239
Super Smash Bros
hungrybox396
Heroes of the Storm
Grubby3383
Trikslyr62
Other Games
summit1g3625
FrodaN1712
C9.Mang0226
KnowMe159
PPMD35
CosmosSc2 16
Organizations
Other Games
gamesdonequick1290
StarCraft 2
CranKy Ducklings9
[ Show 16 non-featured ]
StarCraft 2
• musti20045 30
• CranKy Ducklings SOOP4
• AfreecaTV YouTube
• intothetv
• Kozan
• IndyKCrew
• Migwel
StarCraft: Brood War
• iopq 14
• BSLYoutube
• STPLYoutube
• ZZZeroYoutube
League of Legends
• Nemesis2747
• Jankos2281
• Scarra1089
Other Games
• Shiphtur644
• imaqtpie625
Upcoming Events
FEL
9h 58m
Patches Events
13h 58m
AI Arena Tournament
17h 58m
FEL
1d 10h
Sparkling Tuna Cup
1d 10h
Replay Cast
1d 23h
WardiTV Weekly
2 days
IntoTheTV X SOOP
3 days
ByuN vs Lambo
MaxPax vs Bunny
PiGosaur Cup
4 days
The PondCast
4 days
[ Show More ]
Kung Fu Cup
4 days
IntoTheTV X SOOP
5 days
SHIN vs GuMiho
Clem vs Classic
WardiTV Invitational
6 days
Epic.LAN
6 days
Liquipedia Results

Completed

Proleague 2026-10-22
Blizzard Classic Cup 2026
HCC Season 3

Ongoing

Acropolis #5
KCM Race Survival 2026 Season 4
Acropolis #5 - GSC
1win Private Club #2
Thunderpick World Champ. '26
ESL Pro League Season 24
Stake Ranked Episode 4
1win Private Club #1
Logitech G Play Connect 2026
SL StarSeries Fall 2026
FISSURE Playground #3
BLAST Open Fall 2026
Esports World Cup 2026

Upcoming

BSL Season 23
IPSL Winter 2026-27
SC4ALL II: Brood War
BSL 23: Non-Korean Championship
HSC XXX
Stellar Fest 2: Lunar Cup
SC4ALL II: StarCraft II
Kung Fu Cup 2026 Grand Finals
RSL Offline Finals
eXTREMESLAND 2026
PGL Major Singapore 2026
Stake Ranked Episode 6
BLAST Rivals Fall 2026
IEM Beijing 2026
Stake Ranked Episode 5
PGL Masters Bucharest 2026
TLPD

1. ByuN
2. TY
3. Dark
4. Solar
5. Stats
6. Nerchio
7. sOs
8. soO
9. INnoVation
10. Elazer
1. Rain
2. Flash
3. EffOrt
4. Last
5. Bisu
6. Soulkey
7. Mini
8. Sharp
Sidebar Settings...

Advertising | Privacy Policy | Terms Of Use | Contact Us

Original banner artwork: Jim Warren
The contents of this webpage are copyright © 2026 TLnet. All Rights Reserved.