Well, this is getting better, but still doesn't really match the algorithm. You have eliminated a lot of unnecessary reads, but you still have an O(n*m) solution, which can be improved on greatly. To get around this (and make the code much cleaner), you need to implement the hashing step I outlined in the above node.

Here's just a small snippet to get you thinking. This does the setup of the %del hash.

# Step 2
my %del;
open my $dellist, '<', $delfile or die "Could not open $delfile: $!\n"
+;
for (<$dellist>) { chomp; $del{$_} = 1; }
close $dellist; # Step 3

[download]

Now the 'key' bit (if you'll pardon the pun) is that you never, ever have to iterate through that list again, or open the del file again.

Step 4 is where you iterate through your org list. The setup will be similar to the del list, except that for each line in your org list, you just need to check whether it exists in your %del hash and act accordingly. For instance, exists $del{1234} returns true if and only if `1234' is a key in your %del hash. Read the exists page for more detail.

From your code it looks like you have influence from other structured programming languages. (Are you perhaps thinking that unlink is something like C's free(3) to free allocated memory? You don't need to do that in Perl; it handles garbage collection for you automatically.)

That influence from other languages will certainly help you, but Perl has rich features that you'll want to take advantage of. For instance, the introduction on hashes could be sort of life changing if you're coming from a language that doesn't have a built-in hash/associative array data type.

In reply to Re^3: Search and Remove by rjt
in thread Search and Remove by PyrexKidd

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