How to print the array element values in array order? - perl

Question

How to print the array's values in order of array element?
#ab= <DATA>;
print "#ab\n";
#a = qw(a b c d);
foreach $s(#ab){
foreach $m (#a){
$z =~m/$m/g;
print "$z";
}
}
__DATA__
d 43
a 5
b 24
d 4
a 12
b 54
c 11
a 1
d 1
a 32
In this program gives outputs but i expect the outputs is
a 5
a 12
a 1
a 32
b 24
b 54
c 11
d 43
d 4
d 1
First prints the first array element's matching value then second and so on.. How can i do this?

Answer 1

Your outer loop should loop over #a and inner over #ab
my #ab= <DATA>;
my #a = qw(a b c d);
foreach my $m (#a) {
foreach my $s (#ab) {
print $s if $s =~ /^$m/;
}
}
__DATA__
d 43
a 5
b 24
d 4
a 12
b 54
c 11
a 1
d 1
a 32
output
a 5
a 12
a 1
a 32
b 24
b 54
c 11
d 43
d 4
d 1

Answer 2

It looks like you're trying to sort the array alphabetically but only based on the first letter. I think this does what you want:
use strict;
use warnings;
print sort { (substr $a, 0, 1) cmp (substr $b, 0, 1) } <DATA>;
__DATA__
d 43
a 5
b 24
d 4
a 12
b 54
c 11
a 1
d 1
a 32
Output:
a 5
a 12
a 1
a 32
b 24
b 54
c 11
d 43
d 4
d 1

Answer 3

Try:
#ab= <DATA>;
#a = qw(a b c d);
print map { $tmp = $_; grep { $tmp eq (split(" ", $_))[0] } #ab } #a;
__DATA__
d 43
a 5
b 24
d 4
a 12
b 54
c 11
a 1
d 1
a 32
Explanation
map { ... } #a: loop through each element in array #a, orderly.
$tmp = $_: save the current value of $_ of map function to variable $tmp.
grep { $tmp eq (split(" ", $_))[0] } #ab: with each element in array #ab, we split it to get only the first character, compare with current $tmp value. If equal, grep return that element.

Answer 4

Group the sections, and then print
use strict;
use warnings;
my %group;
while (<DATA>) {
my ($key) = split ' ';
push #{$group{$key}}, $_;
}
for my $key (sort keys %group) {
print #{$group{$key}};
}
__DATA__
d 43
a 5
b 24
d 4
a 12
b 54
c 11
a 1
d 1
a 32
Outputs:
a 5
a 12
a 1
a 32
b 24
b 54
c 11
d 43
d 4
d 1

Answer 5

This scales better than Сухой27's answer: O(S) instead of O(ID*S).
my #ids = qw( a b c d );
my %s_by_id;
while (my $s = <DATA>) {
my ($id) = $s =~ /^(\S+)/
or next;
push #{ $s_by_id{$id} }, $s;
}
for my $id (#ids) {
print #{ $s_by_id{$id} } if $s_by_id{$id};
}