Susquehanna International Group (SIG) Interview Question: A king wants to hold a party,... | Glassdoor

Interview Question

Trading Intern Interview(Student Candidate) Dublin, Co. Dublin (Ireland)

A king wants to hold a party, for which he has 8 kegs of

  wine, one of which he knows is poisoned. If someone consumes any of the poisoned wine, he will drop dead in exactly one months time. The king has 3 servants who have volunteered their lives to test the kegs of wine. What is the shortest amount of time in which the king can identify which keg of wine is poisoned and dispose of it so he can hold the party.
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brain teaser
Answer

Interview Answer

4 Answers

8

One month:

Label the kegs 1-8, each servant has a glass of wine which is a mixture of four of the kegs:

Servant one has a glass consisting of wine from kegs 1, 2, 3 and 4.

Servant two has a glass consisting of wine from kegs 2, 3, 5 and 6.

Servant three has a glass consisting of wine from kegs 3, 4, 6 and 7.

We then wait one month.

If only servant one dies, keg 1 is poisoned.

If servants one and two die, keg 2 is poisoned.

If servants one, two and three die, keg 3 is poisoned.

If servants one and three die, keg 4 is poisoned.

If only servant two dies, keg 5 is poisoned.

If servants two and three die, keg 6 is poisoned.

If only servant three dies, keg 7 is poisoned.

If no one dies, keg 8 is poisoned.

Interview Candidate on Feb 11, 2014
1

Hi,
I also had an interview with SIG recently, and I'm just wondering how long it took for them to give you a job offer after you're final interview

Anonymous on Mar 6, 2014
2

Hi, think my final interview was 22nd Jan and they got back to me 10th Feb or so

Tim on Mar 7, 2014
2

With three tasters, you get 2^3 = 8 bits of information, so you should be able to do it in one month. Specifically, label the kegs 0,1,2,3,4,5,6,7, and note that in base 2:

0 = 000
1 = 001
2 = 010
3 = 011
4 = 100
5 = 101
6 = 110
7 = 111

Each taster takes a place ("column"), i.e. taster 1 drinks 4,5,6,7, 2 drinks 2,3,6,7, 3 drinks 1,3,5,7. Clearly, the combination of tasters that die in a month uniquely determines the poisoned keg

Anonymous on Aug 15, 2016

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