Re: intersection of N arrays

This one takes care of that pesky "more than one instance of X in array Y" test case:

use strict;
our %ids;

sub intersect
{
    my %count;
    my @ret;
    my $count = scalar keys %ids;
    foreach my $key (keys %ids) {
        my %this;
        for (@{$ids{$key}}) {
            next if $this{$_};
            $count{$_}++;
            $this{$_}++;
            if ($count{$_} == $count) {
                push @ret, $_;
            }
        }
    }

    undef %ids;
    return @ret;
}


$ids{'foo'} =  [ 3, 4, 4, 5 ];
$ids{'bar'} =  [ 3 ];
$ids{'zoo'} =  [ 3, 4, 5 ];

print "[ ",join(', ',intersect)," ]\n"; # prints "[ 3 ]"
[download]

Comment on Re: intersection of N arrays Download Code

Replies are listed 'Best First'.
Re^2: intersection of N arrays by Solo (Deacon) on Jul 01, 2004 at 13:29 UTC
The line `next if $this{$_};` [download] should test existence rather than truth, like so `next if exists $this{$_};` [download] --Solo -- You said you wanted to be around when I made a mistake; well, this could be it, sweetheart.	[reply] [d/l] [select]
Re^2: intersection of N arrays by Anonymous Monk on Aug 24, 2020 at 02:55 UTC
This works with numbers, how can you make it work with strings.	[reply]
Re^3: intersection of N arrays by AnomalousMonk (Archbishop) on Aug 24, 2020 at 04:32 UTC
`c:\@Work\Perl\monks>perl use strict; use warnings; my %ids; sub intersect { my %count; my @ret; my $count = keys %ids; foreach my $key (keys %ids) { my %this; for (@{$ids{$key}}) { next if $this{$_}; $count{$_}++; $this{$_}++; if ($count{$_} == $count) { push @ret, $_; } } } undef %ids; return @ret; } $ids{'foo'} = [ qw(three four four five) ]; $ids{'bar'} = [ qw(three) ]; $ids{'zoo'} = [ qw(five four three) ]; print "[ ",join(', ',intersect)," ]\n"; __END__ [ three ]` [download] Give a man a fish: `<%-{-{-{-<`	[reply] [d/l] [select]