### Re^2: CarTalk Puzzler

by Perl Mouse (Chaplain)
 on Nov 17, 2005 at 09:51 UTC ( #509348=note: print w/replies, xml ) Need Help??

in reply to Re: CarTalk Puzzler

The trouble with enumerating the result - what if it had been 2,000,000,000,000,000,000,000 instead of 20,000?
2,000,000,000,000,000,000,000 == 2 * 1021 == 5 * 4 * 1020 == 5 * (2 * 1010)2.

So, all you need to do is list the squares of all numbers from 1 to sqrt(5) * 2 * 1010. It'll take a while to list, but you can do it with a one-liner.

Perl --((8:>*

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Re^3: CarTalk Puzzler
by thor (Priest) on Nov 17, 2005 at 12:51 UTC
I think the OP was saying "what if the original solutions posted in this thread were used for <insert really large number here> bulbs?". The solutions posted near the top of the thread relied on walking the list numerous times, which is infeasible if the list is super large. The elegance in finding the mathematical property for the bulbs being on is that it does scale.

thor

Feel the white light, the light within
Be your own disciple, fan the sparks of will
For all of us waiting, your kingdom will come

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