Sorting a list and removing duplicate elements

texuser74 has asked for the wisdom of the Perl Monks concerning the following question:

Dear Perl Experts,

I have a list of names followed by their page numbers

e.g.

Chee S. L. 8
Cheng T. H. 5
Cheng T. H. 2
Chetan M. 4
[download]

I want to remove the duplicate occurance of the names and arrange the numbers in the following way

required ouput:

Chee S. L. 8
Cheng T. H. 2,5
Chetan M. 4
[download]

Please advice me how to achieve this.

Thanks in advance

_{janitored by ybiC: Renamed from "sorting", because one-word nodetitles hinder site search}

Comment on Sorting a list and removing duplicate elements Select or Download Code

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Re: Sorting a list and removing duplicate elements by hardburn (Abbot) on Aug 17, 2004 at 16:34 UTC
Whenever you think about "remove duplicates" in Perl, think hashes. In this case, you probably want to have each hash entry be an array containing the numbers: `my %data; while(<>) { chomp; my ($name, $number) = $_ =~ /\A (\D+) (\d+) \z/x; push @{ $data{$name} }, $number if $name && $number; }` [download] "There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.	[reply] [d/l]
Re: Sorting a list and removing duplicate elements by davorg (Chancellor) on Aug 17, 2004 at 16:40 UTC
`#!/usr/bin/perl use strict; use warnings; my %data; while (<DATA>) { chomp; next unless /\S/; my ($name, $num) = /(.)\s+(\d+)/; push @{$data{$name}}, $num if ($name && $num); } foreach my $name (sort keys %data) { print "$name "; print join ',', sort { $a <=> $b } @{$data{$name}}; print "\n\n"; } __END__ Chee S. L. 8 Cheng T. H. 5 Cheng T. H. 2 Chetan M. 4` [download] -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club."* -- Chip Salzenberg	[reply] [d/l]
Re: Sorting a list and removing duplicate elements by Anonymous Monk on Aug 17, 2004 at 16:55 UTC
wonderful, your code does the magic thank you very much	[reply]
Re^2: Sorting a list and removing duplicate elements by texuser74 (Monk) on Aug 19, 2004 at 10:29 UTC
Thank you for your help, but one more difficulty i have how to remove the duplicate numbers, e.g. Cheng T. H. 2,2,5 Chetan M. 4 this one should be as Cheng T. H. 2,5 Chetan M. 4 i.e. here i want to remove 2 from first entry Thanks in advance	[reply]
Re^3: Sorting a list and removing duplicate elements by davorg (Chancellor) on Aug 19, 2004 at 10:41 UTC
Change ${data}{$name} to be a hash instead of an array. `#!/usr/bin/perl use strict; use warnings; my %data; while (<DATA>) { chomp; next unless /\S/; my ($name, $num) = /(.)\s+(\d+)/; $data{$name}{$num} = 1; } foreach my $name (sort keys %data) { print "$name "; print join ',', sort { $a <=> $b } keys %{$data{$name}}; print "\n\n"; } __END__ Chee S. L. 8 Cheng T. H. 5 Cheng T. H. 2 Chetan M. 4 Cheng T. H. 2` [download] -- <http://www.dave.org.uk> "The first rule of Perl club is you do not talk about Perl club."* -- Chip Salzenberg	[reply] [d/l]
Re: Sorting a list and removing duplicate elements by pbeckingham (Parson) on Aug 17, 2004 at 16:43 UTC
Use a hash. `#! /usr/bin/perl -w use strict; my %data; while (<DATA>) { my ($name, $page) = /^(.*?)\s+(\d+)$/; push @{$data{$name}}, $page; } print $_, ' ', join (',', sort @{$data{$_}}), "\n" for sort keys %da +ta; __DATA__ Chee S. L. 8 Cheng T. H. 5 Cheng T. H. 2 Chetan M. 4 __OUTPUT__ Chee S. L. 8 Cheng T. H. 5,2 Chetan M. 4` [download] pbeckingham - typist, perishable vertebrate.	[reply] [d/l]