From: tmoran@acm.org
Subject: Re: writing an "artful" algorithm
Date: Fri, 18 Apr 2003 05:51:57 GMT
Date: 2003-04-18T05:51:57+00:00 [thread overview]
Message-ID: <1oMna.263929$Zo.51799@sccrnsc03> (raw)
In-Reply-To: 9BLna.232134$OV.289871@rwcrnsc54
> > 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.
next prev parent reply other threads:[~2003-04-18 5:51 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-17 15:12 writing an "artful" algorithm John Stoneham
2003-04-17 22:08 ` Samuel Tardieu
2003-04-17 22:17 ` Samuel Tardieu
2003-04-18 4:57 ` Steve
2003-04-18 5:51 ` tmoran [this message]
2003-04-22 20:38 ` Dan Eilers
2003-04-23 13:12 ` John Stoneham
2003-05-19 23:19 ` John Atwood
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