$VAR1 = [
'830974',
'722065',
'722046',
'716963'
];
如何计算值为"722065"的数组索引?
firstidx
函数可以帮助解决问题:use strict;
use warnings;
use List::MoreUtils qw(firstidx);
my @nums = ( '830974', '722065', '722046', '716963' );
printf "item with index %i in list is 722065\n", firstidx { $_ eq '722065' } @nums;
__END__
使用List::Util
,它是一个核心模块,不同于List::MoreUtils
,后者并非核心模块:
use List::Util qw(first);
my @nums = ( '830974', '722065', '722046', '716963' );
my $index = first { $nums[$_] eq '722065' } 0..$#nums;
以下是如何查找给定值出现的所有位置:
#!/usr/bin/perl
use strict;
use warnings;
my @x = ( 1, 2, 3, 3, 2, 1, 1, 2, 3, 3, 2, 1 );
my @i = grep { $x[$_] == 3 } 0 .. $#x;
print "@i\n";
如果你只需要第一个索引,你应该使用List::MoreUtils::first_index。
firstidx
。use strict;
use warnings;
use Data::Dumper;
# Index an array with unique elements.
my @var_uniq = qw( 830974 722065 722046 716963 );
my %index_uniq = map { $var_uniq[$_] => $_ } 0..$#var_uniq;
# You could use hash slice assinment instead of map:
# my %index_uniq;
# @index_uniq{ @var_uniq } = 0..$#var_uniq
my $uniq_index_of_722065 = $index_uniq{722065};
print "Uniq 72665 at: $uniq_index_of_722065\n";
print Dumper \%index_uniq;
# Index an array with repeated elements.
my @var_dupes = qw( 830974 722065 830974 830974 722046 716963 722065 );
my %index_dupes;
for( 0..$#var_dupes ) {
my $item = $var_dupes[$_];
# have item in index?
if( $index_dupes{$item} ) {
# Add to array of indexes
push @{$index_dupes{$item}}, $_;
}
else {
# Add array ref with index to hash.
$index_dupes{$item} = [$_];
}
}
# Dereference array ref for assignment:
my @dupe_indexes_of_722065 = @{ $index_dupes{722065} };
print "Dupes 722065 at: @dupe_indexes_of_722065\n";
print Dumper \%index_dupes;
my $VAR1 = [ '830974', '722065', '722046', '716963' ];
my %reverse;
$reverse{$VAR1->[$_]} = $_ for 0 .. @$VAR1 - 1;
print $reverse{722065};
这并不考虑具有重复值的数组。我不建议在生产代码中使用此解决方案。
请查看Perl FAQ。
use strict;
use Data::Dumper;
sub invert
{
my $i=0;
map { $i++ => $_ } @_;
}
my @a = ('a','b','c','d','e');
print Dumper @a;
print Dumper invert @a;
my($index) = grep {$array[$_] ~~ $element} 0..$#array;
。请参见此处:https://dev59.com/pnA75IYBdhLWcg3wkZ-A#3222653 - mivk