Question

I have an array of this kind

@uniqarr = qw(error 0 goodrecordno:6123, error 0 goodrecordno:6143, error 1 goodrecordno:10245, error 1 goodrecordno:10678, error 1 goodrecordno:10698, error 2 goodrecordno:16245, error 2 goodrecordno:16123);

I want the o/p as

error 0 goodrecordno:6123
error 1 goodrecordno:10245 
error 2 goodrecordno:16123

i.e each error onetime with its corresponding lowest recordno.
Can anyone help me without using cpan modules

Thanks in advance.

Answer 1

This is the basic minimum-maximum problem that you’ll find in beginning Perl books. You make one pass through all the elements and remember which one was the lowest as you go along. This is much better than sorting, which is designed for you to put all the elements in order, which is not what you are after.

use strict;
use warnings;

# I'll assume those commas were a mistake. You don't need to separate
# items with commas in a quotewords list
# If I'm wrong, the process is the same although the data massaging
# will be a little different
my @elements = qw(
    error 0 goodrecordno:6123
    error 0 goodrecordno:6143
    error 1 goodrecordno:10245 
    error 1 goodrecordno:10678 
    error 1 goodrecordno:10698 
    error 2 goodrecordno:16245 
    error 2 goodrecordno:16123
    );

my %lowest;
while( my( $error, $number, $goodrecno ) = splice @elements, 0, 3, () )
    {
    my( $recno ) = $goodrecno =~ /(\d+)/;

    # This hash remembers the lowest $recno. If you find another
    # a lower number, you replace the previous value.
    $lowest{$number} = $recno if( 
        ! exists $lowest{$number} 
            ||
        $recno < $lowest{$number}
        );
    }

Once you’ve created the hash that has the lowest elements, you just print it:

foreach my $number ( sort { $a <=> $b } keys %lowest ) {
    print "error $number goodrecordno:$lowest{$number}\n";
    };

This give you the output that you were looking for:

error 0 goodrecordno:6123
error 1 goodrecordno:10245
error 2 goodrecordno:16123

This is a basic template for these sorts of problems. Step 1: scan the data to remember what you want, using a hash to key those data. Step 2: output the contents of the hash.