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        riddles >> cs >> a problem about elevator
        
(Message started by: cuckoo on Jul 11th, 2007, 6:01am)
Title: a problem about elevator
Post by cuckoo on Jul 11th, 2007, 6:01am
You are at the bottom of the elevator shaft of a 100 story building. You see 21 wires labeled 1...21. The wires go up to the 100th floor where the ends are labeled A...U, but you don't know how they correspond to the ends at the bottom. You have a battery, a light bulb, and many small wires. How can you determine the pairing between the numbers and letters by only making one trip to the 100th floor and back down?

hint: 21 is a triangular number, that is 21=1+2+...+6.

can anybody give a solution for any n that is not a triangular number?
Title: Re: a problem about elevator
Post by SMQ on Jul 11th, 2007, 10:41am
Looks like a variation on the 1000 Wires (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1028323982) problem in the hard section.  I believe the solution given by jollytall to this variant (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1151336590;start=2#2) will work for any number of wires > 2.

--SMQ
Title: Re: a problem about elevator
Post by cuckoo on Jul 11th, 2007, 9:53pm
Great! Thank you! ;D
By the way, this website is really cool. I love it!


on 07/11/07 at 10:41:58, SMQ wrote:
Looks like a variation on the 1000 Wires (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1028323982) problem in the hard section.  I believe the solution given by jollytall to this variant (http://www.ocf.berkeley.edu/~wwu/cgi-bin/yabb/YaBB.cgi?board=riddles_hard;action=display;num=1151336590;start=2#2) will work for any number of wires > 2.

--SMQ


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