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Topic: 3 VEnding Machines (Read 13802 times) |
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Moonz
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Was asked this in an interview at MS this week
3 Vending Machines painted BLACK. 3 LABELS : COKE, SPRITE, COKE+SPRITE. ALL machines are labelled incorrect. One can is for a quarter. How many quarters do you need to find the correct labels for each machine ?? I figured out the answer but just for FYI sakes , This forum helped me a lot !! so trying to repay back ... 
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wowbagger
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Re: 3 Vending Machines
« Reply #1 on: Aug 7th, 2003, 8:21am » |
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Depends on how many quarters you have to feed the machines with to get something out of them... 
Anyway, this is along the same lines as Apples and Oranges, only with less information to start with.
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| « Last Edit: Aug 7th, 2003, 8:23am by wowbagger » |
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Icarus
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Re: 3 VEnding Machines
« Reply #2 on: Aug 7th, 2003, 6:19pm » |
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It could take lots. You, after reading the A&O thread, smugly put your quarter in to the "C+S" machine, knowing that if it gives you a Coke, it must be the Coke machine, the "Sprite" machine must really be the C+S machine, and the "Coke" machine would be the Sprite machine. And vice versa, if it gives a sprite. But your whole theory is shot to hell when that Pepsi drops out! 
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James Fingas
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Re: 3 VEnding Machines
« Reply #3 on: Aug 8th, 2003, 7:13am » |
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None. Just label them all "Assorted".
Alternately:
None. Open up the machines, and label them according to what's inside them.
Or:
None. Just pull the plugs out of their sockets, cut the plugs off the cords, and label the machines "Out of Order".
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Doc, I'm addicted to advice! What should I do?
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otter
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Re: 3 VEnding Machines
« Reply #4 on: Aug 8th, 2003, 12:10pm » |
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Alternately:
None. Ignore the three machines and look for one that sells Dr. Pepper.
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We shall not cease from exploration. And the end of all our exploring will be to arrive where we started
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somu
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Re: 3 VEnding Machines
« Reply #5 on: Aug 12th, 2003, 6:31am » |
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Only one check is enough to do the job
say three levels are C, S and CS.
take one from C. surely it won't be C. If its S then S-m/c will have obviously CS ( otherwise third machine will be perfect)
and CS m/c will have C.
...
am I right boss ?
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James Fingas
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Re: 3 VEnding Machines
« Reply #6 on: Aug 12th, 2003, 10:00am » |
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somu,
Not quite. If you take one from C, it could be a C, because C might contain CS.
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mistysakura
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Re: 3 VEnding Machines
« Reply #7 on: Aug 12th, 2003, 11:08pm » |
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somu, if you get an S, there are at least two cases:
"coke"=Sprite "sprite-coke"=coke "sprite"=sprite-coke
or
"coke"=sprite-coke "sprite-coke"=sprite "sprite"=coke
Now what?
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somu
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Re: 3 VEnding Machines
« Reply #8 on: Aug 13th, 2003, 6:40am » |
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IF C is coming out of C means that is obviously CS. So CS labeled one will be S only (Otherwise S machine will be perfect) And 3rd one is C ... same way
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Icarus
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Re: 3 VEnding Machines
« Reply #9 on: Aug 13th, 2003, 6:59pm » |
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But if S comes out of C, it could be that
"C" = S, "S" = C+S, "C+S" = C,or
"C" = C+S, "S" = "C", "C+S" = C.
Putting a coin in the "C" machine is not the way to go, even if this problem were changed to be equivalent the Apples and Oranges one.
As the problem is stated however, its just as possible that a coin in each machine would yield:
"C" => Dr. Pepper
"S" => Grape Nehi
"C+S" => Barq's
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"Pi goes on and on and on ...
And e is just as cursed.
I wonder: Which is larger
When their digits are reversed? " - Anonymous
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somu
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Re: 3 VEnding Machines
« Reply #10 on: Aug 14th, 2003, 2:42am » |
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Hmm ...
Better to put coin in CS machine only ... then hopefully we can come to the conclusion after one trial only .
If (CS -> C)
CS =C,C=S,S=CS
else
CS=S,S=C,C=CS
Is that fine !!
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Grimbal
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Re: 3 VEnding Machines
« Reply #11 on: Apr 30th, 2004, 4:08pm » |
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You need 3 quarters.
If the label is wrong, you have no idea what the hell these machines are selling. I have never seen a Coke machine painted black. Just get one item from each and glue it on the front of the machine. Maybe a sandwich, a coffee and a pack of condoms.
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| « Last Edit: Oct 6th, 2004, 3:22pm by Grimbal » |
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megadeth
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Re: 3 VEnding Machines
« Reply #12 on: Oct 6th, 2004, 11:21am » |
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my first post here...so go easy one me..
u'll need 1 quarter.
put it in C+S
if C+S ->C then S->C+S and C->S
or
if C+S ->S then S->C and C->C+S
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| « Last Edit: Oct 6th, 2004, 11:23am by megadeth » |
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Rejeev
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Re: 3 VEnding Machines
« Reply #13 on: Oct 11th, 2004, 9:09pm » |
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You need one quarter.
get one can from S.
If it contains C -> CS contains S (because, CS cannot contain CS and C is already at S). And C contains CS.
If S contains CS -> C contains S and CS contains C
Important thing to note here is "all are incorrect"
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Grimbal
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Re: 3 VEnding Machines
« Reply #14 on: Oct 12th, 2004, 10:05am » |
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But if "S contains CS", you will get a C or an S. If you get a C, you won't know whether it contains C or the C+S.
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Icarus
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Re: 3 VEnding Machines
« Reply #15 on: Oct 12th, 2004, 5:28pm » |
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And, as I have hinted at above, the way this puzzle is stated, they need not contain Coke or Sprite at all! Since all you know is that the labels are incorrect, the machines could dispence Moose Juice, Snapple, and Ocean Spray.
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"Pi goes on and on and on ...
And e is just as cursed.
I wonder: Which is larger
When their digits are reversed? " - Anonymous
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Rejeev
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Re: 3 VEnding Machines
« Reply #16 on: Oct 12th, 2004, 9:17pm » |
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on Oct 12th, 2004, 10:05am, Grimbal wrote:But if "S contains CS", you will get a C or an S. If you get a C, you won't know whether it contains C or the C+S.
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Coke + Sprite means Coke sprite mixture (some cocktail!!!) or coke OR Sprite?
Again as Icarus suggested, lebeled incorrect means just incorrect or only labels misplaced?
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Grimbal
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Re: 3 VEnding Machines
« Reply #17 on: Oct 13th, 2004, 1:05am » |
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The way I understand it, the labels have been misplaced an none of them is on its original machine, and the C+S machine contains both types of cans and gives one of them randomly.
When I said it could contain anything, a sandwich etc, I was intentionally misinterpreting the question.
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Rejeev
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Re: 3 VEnding Machines
« Reply #18 on: Oct 13th, 2004, 1:14am » |
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on Oct 13th, 2004, 1:05am, Grimbal wrote:The way I understand it, the labels have been misplaced an none of them is on its original machine, and the C+S machine contains both types of cans and gives one of them randomly.
When I said it could contain anything, a sandwich etc, I was intentionally misinterpreting the question. |
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In this case also you need only one quarter.
First put one quarter into C+S machine
if that gives C, then S is C+S and C is S
if that gives S, then C is C+S and S is C
(it cannot give C+S because it is labeled C+S)
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Dave
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Re: 3 VEnding Machines
« Reply #19 on: May 25th, 2009, 10:20pm » |
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You may not need any quarters!
Google "soda machine hacks" and you will find that there is a sequence of pushbutton presses that will show you what is in the machine (among other things!)
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chronodekar
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Re: 3 VEnding Machines
« Reply #20 on: Jun 24th, 2009, 2:38am » |
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If in the question, "labels are incorrect" means that the original labels could be anything, then the rest of the statements in the question are pointless.
Intuitively, that means we can assume that the 3 labels have been switched around AND that none of them are on the machines that they correspond to.
Furthermore, at an interview, telling the questioner that Pepsi might come out, should, IMO, significantly reduce the chances of you being selected.
So, everything taken into account my answer is,
for reasons mentioned in an earlier post.
-chronodekar
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cynder
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Re: 3 VEnding Machines
« Reply #21 on: May 28th, 2010, 7:04pm » |
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on Apr 30th, 2004, 4:08pm, grimbal wrote:You need 3 quarters.
If the label is wrong, you have no idea what the hell these machines are selling. I have never seen a Coke machine painted black. Just get one item from each and glue it on the front of the machine. Maybe a sandwich, a coffee and a pack of condoms. |
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In this misinterpertation you would need an infinite amount of quarters actually. Since a machine could be selling coffee+ sandwhich+ condoms+ ........ etc.
Id rather go for .
On a serious note, would interviewers appreciate you pointing out an ill-defined question? Or would they rather have you just awnser it as it was obviously intended.
Did anyone have experience with this?
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| « Last Edit: May 28th, 2010, 7:05pm by cynder » |
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