Question

In this script

#!/usr/bin/perl -w

use strict;

my @ar = (1,2,10,3,5);

@ar = sort {$a <=> $b} @ar;

does @ar now contain (1,2,3,5,10).

Now would I like to get the inverse array i.e. (4,6,7,8,9).

Any suggestions how that can be done?

Answer 1

When working with set operations, hashes work well:

my %have = map {$_ => 1} @ar;

my @inv  = grep {not $have{$_}} 1 .. 10;

print "@inv\n"; # 4 6 7 8 9

If you will not know the bounds before hand, and would like to determine them from the min/max of @ar, since its sorted that becomes easy:

my @inv = grep {not $have{$_}} $ar[0] .. $ar[-1];