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From: tmoran@acm.org
Newsgroups: comp.lang.ada
Subject: Re: writing an "artful" algorithm
References: <9BLna.232134$OV.289871@rwcrnsc54>
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Date: 2003-04-18T05:51:57+00:00
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> > there is the condition that no digit can be repeated in either 5-digit
> > number, and all the digits in the product must be unique. One
>
> The approach used here is to generate a list containing all 5 digit numbers
> containing unique digits.  Then sequence through the list generating
> products and testing the unique digits condition on the product.
  Clearly (casting out nines) the product must be a multiple of 9, so
either one of the multipliers is a multiple of 9, ie sum of its digits
mod 9 = 0, or both are multiples of 3, ie, sum of digits mod 3 = 0.
That should reduce the number of trial multiplies.