Re: Mathematics ethics

it took me quite a lot to understand that you were talking about narcissistic numbers (thanks Thelonius!).

that said, your script does not work. the while loop should look like:

while ( $vlnum > 0 ) {
    $vldig = $vlnum % 10; 
    $vlsum = $vlsum + ($vldig * $vldig * $vldig);
    $vlnum = $vlnum / 10;
}
[download]

as for simplicity, I would do it like this:

#!/usr/bin/perl -w

use strict;

my $vlnum = 0;
my $vlsum = 0;

print "Insert a number: ";
chomp ( $vlnum = <STDIN> );

# map { $vlsum += $_ ** 3 } split //, $vlnum;
# oops, this should be (thanks [broquaint]!):

$vlsum += $_ ** 3 for split //, $vlnum;

if ( $vlsum == $vlnum ) { 
    print "Is narc dude!"; 
} else { 
    print "Try another number!"; 
}
[download]

cheers,
Aldo

King of Laziness, Wizard of Impatience, Lord of Hubris

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Re: Re: Mathematics ethics
by RMGir (Prior) on Oct 28, 2002 at 16:00 UTC

And in that case, there's a nice complete list available as a link from that page, so you can just do it by table lookups.

#!/usr/bin/perl -w

# Silly super-efficient interactive narcissistic checker...

use strict;

# http://mathworld.wolfram.com/packages/Narcissistic.dat
my %narcs=map {$_ => 1} (
0,1,2,3,4,5,6,7,8,9,153,370,371,407,1634,8208,9474,54748,92727,93084,
548834,1741725,4210818,9800817,9926315,24678050,24678051,88593477,
146511208,472335975,534494836,912985153,4679307774,32164049650,
32164049651,40028394225,42678290603,44708635679,49388550606,
82693916578,94204591914,28116440335967,4338281769391370,
4338281769391371,21897142587612075,35641594208964132,35875699062250035
+,
1517841543307505039,3289582984443187032,4498128791164624869,
4929273885928088826,63105425988599693916,128468643043731391252,
449177399146038697307,21887696841122916288858,27879694893054074471405,
27907865009977052567814,28361281321319229463398,
35452590104031691935943,174088005938065293023722,
188451485447897896036875,239313664430041569350093,
1550475334214501539088894,1553242162893771850669378,
3706907995955475988644380,3706907995955475988644381,
4422095118095899619457938,121204998563613372405438066,
121270696006801314328439376,128851796696487777842012787,
174650464499531377631639254,177265453171792792366489765,
14607640612971980372614873089,19008174136254279995012734740,
19008174136254279995012734741,23866716435523975980390369295,
1145037275765491025924292050346,1927890457142960697580636236639,
2309092682616190307509695338915,17333509997782249308725103962772,
186709961001538790100634132976990,186709961001538790100634132976991,
1122763285329372541592822900204593,12639369517103790328947807201478392
+,
12679937780272278566303885594196922,
1219167219625434121569735803609966019,
12815792078366059955099770545296129367,
115132219018763992565095597973971522400,
115132219018763992565095597973971522401);

while(<>) {
    chomp;
    if(exists $narcs{$_}) {
        print "Is narc, dude\n";
    }
    else {
        print "Not narc, please try again\n";
    }
}
[download]

But if it's really numbers equal to the sum of their digits ** 3, then I'm not sure what the exhaustive list would look like...

I think there WOULD be one, though, since 9**3 is only 729, so that limits how big your number could be. So you could still precompute the possible answers, if you needed an efficient way to answer this question...

Hehe, it doesn't seem to be a problem that cries out for optimization, does it? :)
--
Mike

[reply]
[d/l]


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