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Re: list of four digit lock combinations without repeated digits

by johngg (Canon)
on Jun 22, 2018 at 16:22 UTC ( #1217223=note: print w/replies, xml ) Need Help??


in reply to list of four digit lock combinations without repeated digits

Here are a couple of nested loop solutions that are probably what the *::Combinatorics modules do under the hood.

johngg@abouriou ~/perl/Monks $ perl -Mstrict -Mwarnings -E ' for my $w ( 0 .. 6 ) { for my $x ( $w + 1 .. 7 ) { for my $y ( $x + 1 .. 8 ) { for my $z ( $y + 1 .. 9 ) { say join q{}, $w, $x, $y, $z; } } } }' | wc -l 210
johngg@abouriou ~/perl/Monks $ perl -Mstrict -Mwarnings -E ' say for map { my $w = $_; my $x = $w + 1; map { my $y = $_ + 1; map { my $z = $_ + 1; map { join q{}, $w, $x, $y, $z } $z .. 9 } $y .. 8 } $x .. 7 } 0 .. 6;' | wc -l 210

Done just for fun, the modules are probably the best way to go.

Update: Ignore the map version as it is giving incorrect results, right number but wrong digits.

Update 2: Spotted my error in the map version, I was initialising the three inner variables too early. This works:-

johngg@abouriou ~/perl/Monks $ perl -Mstrict -Mwarnings -E ' say for map { my $w = $_; map { my $x = $_; map { my $y = $_; map { my $z = $_; join q{}, $w, $x, $y, $z; } ( $y + 1 ) .. 9 } ( $x + 1 ) .. 8 } ( $w + 1 ) .. 7 } 0 .. 6;' | wc -l 210

Cheers,

JohnGG

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