How can I compare two arrays with alphanumeric elements? - perl

Question

I have two arrays that I want to compare
#array1 = ( aaa, bbb, aaabbb, aaa23bbb, ddd555, 430hd9789);
#array2 = ( 34322hh2, jjfjr78, uuu7shv, ddd555, hjkdjroo);
I have to compare these two arrays and find duplicate and do something about it.
Conditions:
Length of each element in array can be different. There is no such fixed pattern.
Elements can be just numeric i.e. 334343, or just char i.e. "somewordexample", or it can alphanumeric i.e. wewe83493
There can be more such elements in the array.
Now I know the following about comparison operators == and eq:
== is for comparing numbers
eq is for string comparison
How can I compare alphanumeric values?
This is my code so far
for (my $i = 0 ; $i <= $#array1 ; $i++ ) {
for (my $j = 0 ; $j <= $#array2 ; $j++ ) {
if ( $array1[$i] == $arra2[$j] ) {
print "duplicate";
}
}
}

Answer 1

You manner is indolent, and you seem to be looking for a quick fix without caring whether you understand the solution. The posts on Stack Overflow are primarily for people other than the originator who may have a similar problem.
You should read perlfaq4. Specifically:
perldoc -q intersection - "How do I compute the difference of two arrays? How do I compute the intersection of two arrays?"
perldoc -q contained - "How can I tell whether a certain element is contained in a list or array?"
perldoc -q duplicate - "How can I remove duplicate elements from a list or array?"

Answer 2

Thank you for posting your misbehaving code.
There are a few problems
You must always use strict and use warnings at the top of every Perl program, and declare each variable as close as possible to its first point of use. That simple measure will reveal many faults for you that you may otherwise overlook
I have used qw to define the array data
It is much better to use the Perl foreach than the C-style for
As you appear to have discovered, the == operator is for comparing numbers. You have strings so you need eq
Apart from that, all I have changed in your code is to mention the text of the duplicate entry instead of just printing "duplicate"
use strict;
use warnings;
my #array1 = qw( aaa bbb aaabbb aaa23bbb ddd555 430hd9789 );
my #array2 = qw( 34322hh2 jjfjr78 uuu7shv ddd555 hjkdjroo );
for my $i (0 .. $#array1) {
for my $j (0 .. $#array2) {
if ( $array1[$i] eq $array2[$j] ) {
print "Duplicate '$array1[$i]'\n";
}
}
}
output
Duplicate 'ddd555'

Answer 3

Your alphanumeric values can still be treated as strings. If you want to find elements that are in both your lists, you can use the get_intersection function provided by the List::Compare module:
use strict;
use warnings;
use List::Compare;
my #array1 = qw(aaa bbb aaabbb aaa23bbb ddd555 430hd9789);
my #array2 = qw(34322hh2 jjfjr78 uuu7shv ddd555 hjkdjroo);
my $comp = List::Compare->new(\#array1, \#array2);
my #duplicates = $comp->get_intersection();
if (#duplicates > 0) {
print "#duplicates\n";
}
Output:
ddd555

Answer 4

Alphanumeric values are just strings. Numeric values are a subset of those that Perl considers to be numeric (i.e. Scalar::Util::looks_like_number() returns true). In this case, you could use eq or any other string-related function for comparison (such as the less commonly used index).
To find exact duplicates in O(n) time
my %seen;
for my $duplicate (grep { ++$seen{$_} > 1 } (#array1, #array2))
{
# Do what you need to do to the duplicates
}
If you just want to get rid of the elements of #array1 that are duplicated in #array2,
my %seen = map { $_ => 1 } #array2;
#array1 = grep { not $seen{$_} } #array1;

Answer 5

you can do this using exact matching regex:
if("4lph4" =~ /^4lph4$/)
{ .... }