Equal prime and composite sums: Difference between revisions

=={{header|Perl}}==

Not especially fast, but minimal memory usage.

{{libheader|ntheory}}

<lang perl>use strict;

use warnings;

use feature <say state>;

use ntheory <is_prime next_prime>;

sub comma { reverse ((reverse shift) =~ s/(.{3})/$1,/gr) =~ s/^,//r }

sub suffix { my($d) = $_[0] =~ /(.)$/; $d == 1 ? 'st' : $d == 2 ? 'nd' : $d == 3 ? 'rd' : 'th' }

sub prime_sum {

state $s = state $p = 2; state $i = 1;

if ($i < (my $n = shift) ) { do { $s += $p = next_prime($p) } until ++$i == $n }

$s

}

sub composite_sum {

state $s = state $c = 4; state $i = 1;

if ($i < (my $n = shift) ) { do { 1 until ! is_prime(++$c); $s += $c } until ++$i == $n }

$s

}

my $ci++;

for my $pi (1 .. 119_000) {

next if prime_sum($pi) < composite_sum($ci);

printf( "%20s - %11s prime sum, %12s composite sum\n",

comma(prime_sum $pi), comma($pi).suffix($pi), comma($ci).suffix($ci))

and next if prime_sum($pi) == composite_sum($ci);

$ci++;

redo

}</lang>

{{out}}

<pre> 10 - 3rd prime sum, 2nd composite sum

1,988 - 33rd prime sum, 51st composite sum

14,697 - 80th prime sum, 147th composite sum

83,292 - 175th prime sum, 361st composite sum

1,503,397 - 660th prime sum, 1,582nd composite sum

18,859,052 - 2,143rd prime sum, 5,699th composite sum

93,952,013 - 4,556th prime sum, 12,821st composite sum

89,171,409,882 - 118,785th prime sum, 403,341st composite sum

9,646,383,703,961 - 1,131,142nd prime sum, 4,229,425th composite sum

209,456,854,921,713 - 5,012,372nd prime sum, 19,786,181st composite sum</pre>