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Re: how do i find common elements of X number of arrays whose names i don't know?

by integral (Hermit)
on Jun 28, 2004 at 08:10 UTC ( #370139=note: print w/replies, xml ) Need Help??

in reply to how do i find common elements of X number of arrays whose names i don't know?

Firstly to find @accessors, you can use the keys function on the %$self hash.

But I'd choose to push the value rather than the key so a loop over values(%$self) might make more sense.

my @tocheck; for my $value (values %$self) { push @tocheck, $value if ref($value) eq 'ARRAY'; } my %seen; for my $array (@tocheck) { $seen{$_}++ for @$array; } return grep { $seen{$_} == @tocheck } keys %seen;

So far we haven't used map (but we did use grep), but we can combine the two loops together so we don't need @tocheck as an intermediate.

my ($n, %seen); for my $array (values %$self) { next unless ref($array) eq 'ARRAY'; # we're only interested in array +s $seen{$_}++ for @$array; $n++; } return grep { $seen{$_} == $n } keys %seen;

Here's a solution using map to replace one of the loops (Update: But it doesn't solve the right problem, since it just checks for duplicates, rather than things appearing multiple times):

my %seen; for my $value ( map { ref($_) eq 'ARRAY' ? @$_ : () } values %$self ) +{ $seen{$value}++; } return grep { $seen{$_} > 1 } keys %seen;

integral, resident of freenode's #perl

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