Re: [Pulze] The Weighing game

[HUNG QUANG NGO <hngo@cs.umn.edu>]

  Chia coins tha`nh 3 nho'm mo^~i nho'm 3 coins. Go.i la` nho'm 1, 2, 3

  DDa(.t nho'm 1 va` 2 le^n 2 ddi~a ca^n, ne^'u chu'ng ba(`ng nhau thi`
ddo^`ng coin gia? o*? nho'm 3. Ne^'u va^.y thi` chi? ca^`n ca^n 2 la^`n
nu*~a la` xong ba(`ng ca'ch dda(.t 2 coins cu?a nho'm 3 le^n ddi~a, ne^'u
chu'ng ba(`ng nhau thi` coin o*? ngoa`i la` gia?, ne^'u chu'ng kha'c nhau
thi` dda(.t ddo^`ng coin o*? ngoa`i vo*`i mo^.t trong 2 ddo^`ng coin o*?
trong le^n dde^? xa'c ddi.nh

  Ne^'u ca^n na(.ng cu?a nho'm 1 va` 2 kha'c nhau , gia? su*? nho'm 2 
na(.ng ho*n,  dda(.t nho'm 1 va` 3 le^n ca^n :

 - Ne^'u nho'm 1 va` 3 ba(`ng nhau thi` ta bie^'t ddo^`ng coin gia? o*?
nho'm 2 va` nhe. ho*n ddo^`ng coin tha^.t. Ne^'u va^.y thi` chi? ca^`n
ca^n mo^.t la^`n nu*~a vo*'i cu`ng kie^?u ca^n (tre^n ca'c coin cu?a
nho'm 2) la` xa'c ddi.nh ddu*o*.c vi` ta dda~ bie^'t ddo^`ng coin gia?
nhe. ho*n.

 - Ne^'u nho'm 1 va` 3 kha'c nhau, va^.y thi` nho'm 1 chu*'a ddo^`ng gia?
va` ddo^`ng gia? na(.ng ho*n ddo^`ng tha^.t. Mo^.t la^`n ca^n nu*~a tre^n
nho'm 1 se~ xa'c ddi.nh ddu*o*.c

 ---

 Nha^n tie^.n dda^y xin cha`o ta^'t ca? ca'c anh chi. va` co^ chu' ba'c.
To^i te^n Ngo^ Quang Hu*ng, ddang ho.c chu*o*ng tri`nh sau dda.i ho.c
(Computer Science) o*? tru*o*`ng Minnesota at Twin Cities. Ho^`i tru*o*'c
to^'t nghie^.p Ba''ch Khoa tpHCM.


> -------------------------------------------------------------------------
> You have 12 coins, labelled A, B, ..., L. One of them is a fake. It is a 
> different weight to the others.
> You also have a pair of scales which you can use to weigh coins against 
> other coins. You are permitted 3 weighings, and you have to identify the 
> fake coin and whether it is lighter or heavier than the genuine coins.
> For each weighing, you have to decide which coins to put on the left 
> scale and which to put on the right scale. You will be told which side is 
> heavier.
> For instance, you may choose to put coins A, B, C on the left scale and 
> D, E, F on the right scale.
> Then if A was the fake and it was lighter, the right scale would go down.
> On the other hand, if the fake was one of G ... L, the scale would stay 
> level. 
> 

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Hung Quang Ngo              | " A man travels far in search
Computer Science Department |   for happiness, and returns
University of Minnesota     |   home to find it "
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