How to Test if Two Arrays are Ordered in the Same Way

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

This is an attempt to save a thread in SoPW which I thought can be useful for others.

There are already incredible answers in the thread, so feel free to check in SoPW.
Please don't misunderstand me. I honestly think this can be useful. I don't mean to boost my XP here, or in that thread which I posted.

Here I wanted to test if an array is of a _same order_ with another, left array is always be greater/superset or equal to the right one. Here is my current code.

#!/usr/bin/perl -w

# The original code here is constructed 
# thanks to ysth's suggestion  

use strict;
my @AR  = qw(a b c);   # First Case
my @ar  = qw(z a b c); # Second Case

my @ar2 = qw(b a);
my @ar3 = qw(a b);
my @ar4 = qw(a b c);
my @ar5 = qw(z a b c);

print "First case\n";
#                   L     R
print test_ordered(\@ar,\@ar2),"\n"; # Answer:False(0)
print test_ordered(\@ar,\@ar3),"\n"; # Answer:True(1)
print test_ordered(\@ar,\@ar4),"\n"; # Answer:True(1)
print test_ordered(\@ar,\@ar5),"\n"; # Answer:True(1)

print "Second case\n";
print test_ordered(\@AR,\@ar2),"\n"; # Answer: False(0)
print test_ordered(\@AR,\@ar3),"\n"; # Answer: True(1)
print test_ordered(\@AR,\@ar4),"\n"; # Answer: True(1)


sub test_ordered
{
    #test if two arrays are ordered in same way
    #assuming no duplicate and left array is always 
    #be greater/superset or equal to the right one

    #    L    R
    my ($ar1,$ar2)= @_;

    my %h;

    @h{@$ar1} = (0..$#{$ar1});
    my $decision = grep($h{$ar2[$_]} != $_, 0..$#{$ar2}) ? 0 : 1;

   return $decision;
}
[download]

Currently the code give correct answer for the Second Case. How can I modify it such that it's also correct for the First Case?
Now it prints:

First Case:       Second Case:
0                 0
0                 1
0                 1
1
[download]

The desired answer is:

First Case:       Second Case:
0                 0
1                 1
1                 1
1
[download]

Regards,
Edward

<code>

Originally posted as a Categorized Question.

Comment on How to Test if Two Arrays are Ordered in the Same Way Select or Download Code

Replies are listed 'Best First'.
Re: How to Test if Two Arrays are Ordered in the Same Way by jdhedden (Deacon) on Jun 06, 2005 at 16:23 UTC
Your decision line needs to be: `my $decision = grep($h{$$ar2[$_-1]} > $h{$$ar2[$_]}, 1..$#{$ar2}) +? 0 : 1;` [download] You have to take into account the elements order with respect to each other. In this case, pos1 <= pos2 <= pos3 ...	[reply] [d/l]
Re: How to Test if Two Arrays are Ordered in the Same Way by monkfan (Curate) on Jun 09, 2005 at 12:23 UTC
Ok, this is one the answer given by most revered tlm to me the other day: `sub test_ordered { my ( $ref, $test ) = @_; # $i scans the indices of @$ref; # $matched keeps count of # of elements matched in @$test; my ( $i, $matched ) = ( 0, 0 ); OUTER: for ( @$test ) { while ( $i < @$ref or return 0 ) { if ( $ref->[ $i++ ] eq $_ ) { last OUTER if ++$matched == @$test; last; } } } return 1; }` [download] More can be found here. Don't vote my root posting but vote those remarkable answers you will find there.	[reply] [d/l]


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