One-two primes: Difference between revisions
Added Perl
(→{{header|Wren}}: Added a generalized version.) |
SqrtNegInf (talk | contribs) (Added Perl) |
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1900: (1 x 1889) 122212212211
2000: (1 x 1989) 122121121211
</pre>
=={{header|Perl}}==
Mostly generalized, but doesn't handle first term of the 0/1 case.
{{libheader|ntheory}}
<syntaxhighlight lang="perl" line>
use v5.36;
no warnings 'recursion';
use ntheory 'is_prime';
sub condense ($n,$a,$b) { my $i = index($n,$b); $i>9 ? "($a x $i) " . substr($n,$i) : $n }
sub combine ($d, $a, $b, $s='') {
if ($d == 1 && is_prime $s.$a) { return $s.$a
} elsif ($d == 1 && is_prime $s.$b) { return $s.$b
} elsif ($d == 1) { return 0
} else { return combine($d-1,$a,$b,$s.$a) || combine($d-1,$a,$b,$s.$b) }
}
my($a,$b) = (1,2);
say "Smallest n digit prime using only $a and $b (or '0' if none exists):";
printf "%4d: %s\n", $_, combine($_,$a,$b) for 1..20;
printf "%4d: %s\n", $_, condense(combine($_,$a,$b),$a,$b) for map {100*$_} 1..20;
($a,$b) = (7,9);
say "\nSmallest n digit prime using only $a and $b (or '0' if none exists):";
printf "%4d: %s\n", $_, condense(combine($_,$a,$b),$a,$b) for 1..20, 100, 200;
# 1st term missing
#($a,$b) = (0,1);
#printf "%4d: %s\n", $_+1, combine($_,$a,$b,1) for 1..19;
</syntaxhighlight>
{{out}}
<pre>
Smallest n digit prime using only 1 and 2 (or '0' if none exists):
1: 2
2: 11
3: 211
4: 2111
5: 12211
6: 111121
7: 1111211
8: 11221211
9: 111112121
10: 1111111121
11: 11111121121
12: 111111211111
13: 1111111121221
14: 11111111112221
15: 111111112111121
16: 1111111112122111
17: 11111111111112121
18: 111111111111112111
19: 1111111111111111111
20: 11111111111111212121
100: (1 x 92) 21112211
200: (1 x 192) 21112211
300: (1 x 288) 211121112221
400: (1 x 390) 2111122121
500: (1 x 488) 221222111111
600: (1 x 590) 2112222221
700: (1 x 689) 21111111111
800: (1 x 787) 2122222221111
900: (1 x 891) 222221221
1000: (1 x 988) 222122111121
1100: (1 x 1087) 2112111121111
1200: (1 x 1191) 211222211
1300: (1 x 1289) 22121221121
1400: (1 x 1388) 222211222121
1500: (1 x 1489) 21112121121
1600: (1 x 1587) 2121222122111
1700: (1 x 1688) 212121211121
1800: (1 x 1791) 221211121
1900: (1 x 1889) 22212212211
2000: (1 x 1989) 22121121211
Smallest n digit prime using only 7 and 9 (or '0' if none exists):
1: 7
2: 79
3: 797
4: 0
5: 77797
6: 777977
7: 7777997
8: 77779799
9: 777777799
10: 7777779799
11: 77777779979
12: 777777779777
13: 7777777779977
14: (7 x 11) 977
15: (7 x 11) 9797
16: (7 x 11) 97799
17: (7 x 15) 97
18: (7 x 13) 97977
19: (7 x 16) 997
20: (7 x 16) 9997
100: (7 x 93) 9979979
200: (7 x 192) 99777779
</pre>
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