in reply to Find the common beginning substring in an array of strings

Assuming a character set with a single-character-to-byte mapping: 

>perl -wMstrict -le
"use List::Util qw(reduce);
 ;;
 my @ra = qw(ABCDxyz  ABCfoo  ABCDEbar);
 ;;
 use vars qw($a $b);
 my $min_start_seq =
   reduce { length($a) < length($b) ? $a : $b }
   map m{ \A \x00* }xmsg,
   map $ra[0] ^ $_,
   @ra
   ;
 my $common_starting_substring = $ra[0] & ~$min_start_seq;
 print qq{'$common_starting_substring'};
"
'ABC'

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Re^2: Find the common beginning substring in an array of strings
by technojosh (Priest) on Jun 06, 2012 at 18:56 UTC
    This is the code that does the trick against all the examples I have so far... I don't have enough time to post it, but there is a 180-element array I have on my laptop that was not working with the code from the other comment. This was just tricky enough that I thought seeing the way some different monks approached it would be fun. I remain open to other solutions, as this is kind of a fun problem to think about.

    Thanks!!

    -TJ
[reply]

      In that case, though I'm certain the masking method others have posted is the best solution, here's a recursive/substr method, just for fun: 

      #!/usr/bin/env perl
use Modern::Perl;

sub findstr {
    if( @_ == 1 ){
        return shift;
    }
    my $x = shift;
    my $y = shift;
    my $l = length $x > length $y ? length $y : length $x;
    for( my $i=$l; $i>0; $i--){
        if( substr($x, 0, $i) eq substr($y, 0, $i)){
            return findstr(substr($x,0,$i), @_);
        }
    }
}

my @array_of_test_names = (
    'History - Family History - Suite with Patient - Clinic - Select R
+emove(-) Icon of Relative. - Clinic',
    'History - Family History - Suite with Patient - Clinic - Save aft
+er Entering values in all fields - Clinic',
    'History - Family History - Suite with Patient - Clinic - Select A
+dd(+) Icon of Relative. - Clinic',
    'History - Family History - Suite with Patient - Clinic - Multiple
+ selection of relatives - Clinic',
    'History - Family History - Suite with Patient - Clinic - Interact
+ion Checking message not provided if procedure code is selected - Cli
+nic',
    'History - Family History - Suite with Patient - Clinic - Interact
+ion Checking message provided if no procedure code is selected - Clin
+ic',
);

my $match = findstr(@array_of_test_names);
say $match;

      [download]

      Aaron B.
      Available for small or large Perl jobs; see my home node.

[reply]
[d/l]
      In that case (and also because I'm only now reading this node), there's this based on a common prefix removal whim I had in the past (with partial credits to moritz for tidying up my original code as seen on my scratchpad): 
      #!/usr/bin/perl

use strict;
use warnings;

my @array_of_test_names = (
                           'History - Family History - Suite with Pati
+ent - Clinic - Select Remove(-) Icon of Relative. - Clinic',
                           'History - Family History - Suite with Pati
+ent - Clinic - Save after Entering values in all fields - Clinic',
                           'History - Family History - Suite with Pati
+ent - Clinic - Select Add(+) Icon of Relative. - Clinic',
                           'History - Family History - Suite with Pati
+ent - Clinic - Multiple selection of relatives - Clinic',
                           'History - Family History - Suite with Pati
+ent - Clinic - Interaction Checking message not provided if procedure
+ code is selected - Clinic',
                           'History - Family History - Suite with Pati
+ent - Clinic - Interaction Checking message provided if no procedure 
+code is selected - Clinic',
                          );

my @second_sample_array = (
                           'WorkCenter - List Patients - To check the 
+items displayed in Filter By combo box',
                           'WorkCenter - List Patients - To check Filt
+er By combo box when no patients are assigned on initial login',
                           'WorkCenter - List Patients - Order in whic
+h patients are displayed',
                          );

sub getleastcommonprefix {
    my @searcharray = @_;
    my $common      = $searcharray[0];
    foreach my $index (1 .. $#searcharray) {
        $_ = $searcharray[0] . reverse $searcharray[$index];
        m/(.*)(.*)(??{quotemeta reverse $1})/s;
        if (length $1 < length $common) {
            $common = $1;
        }
    } ## end foreach my $index (1 .. $#searcharray)
    return $common;
} ## end sub getleastcommonprefix

print 'Common prefix for first sample [' . getleastcommonprefix(@array
+_of_test_names) . "]\n";
print 'Common prefix for second sample [' . getleastcommonprefix(@seco
+nd_sample_array) . "]\n";

      [download]
      Which gives the following output: 
      Common prefix for first sample [History - Family History - Suite with 
+Patient - Clinic - ]
Common prefix for second sample [WorkCenter - List Patients - ]

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[d/l]
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