I'm not sure whether the optimization would contribute much to the overall speedup, but the following two lines do much needless work:

    $s =~ s/\s+/=/g;
    my @v = split( /[\[\],]/, $s ); #create an array from string $s
# assign hash value pairs and insert '=' between them to create phoneb
+ook 
    my %hash = map { split( /=/, $_, $x + 1 ) } @v; 
entry
[download]

Why do you convert all whitespace in $s to = and then split on = again? What use is @v?

Also, the fasted way to do general lookups in Perl is to use a hash. In your case, the fastest data structure to look up the name from a number would be a hash that maps each number to a name:

my %reverse_phonebook = (
    123 => 'jack',
    456 => 'jill',
    ...
);
[download]

Building this data structure allows for quick repeated lookups of names if all you have is the number.

Hi dk27,

Just that in 2 of the test cases, it gets timed out.

I see the following inefficiencies, which I already touched upon:

• Reading the entire input into memory is unnecessary, it is enough to process the input line-by-line.
• As Corion already pointed out, you're doing what appears to be unnecessary work on the input. Unless there are other requirements for the input format that you haven't told us about?
• When looking up a phone number, you're searching the entire @data array twice, first with grep, then with for ( my $m = 0 ; $m <= $len1 ; $m++ ). Also, in the grep you're using a regular expression, which appears unnecessary and takes up CPU cycles since later on you're just doing an exact comparison with if ( $data[$m] eq $N[$i] ).
• Using grep is inefficient for finding a single array element, as it searches the entire array. There would be the alternative first from the core module List::Util, which returns the first match, but if all you need is exact matches, even better would be hash lookups.

Hope this helps,
-- Hauke D

I did get your code to run and produce your desired result although there is a coding mistake here:

# assign hash value pairs and insert '=' between them to create phoneb
+ook 
    my %hash = map { split( /=/, $_, $x + 1 ) } @v; 
entry
[download]

# assign hash value pairs and insert '=' between them to create phoneb
+ook entry
    my %hash = map { split( /=/, $_, $x + 1 ) } @v;
[download]

I don't know what kind of performance or other test case criteria are required. I can only go upon what you have posted. See my code at Re: Perl program to look into the phone directory and in case of a match, print the name along with the number.

In terms of performance, your code besides being pretty obtuse, has many loops and loops within loops.

Some hints:

• Input/Output (I/O) is expensive CPU wise. Even just locating the end-of-line character(s) in an input stream takes CPU power to examine every single input character.
• Looping is "expensive". There are loops within your code that you don't recognize as loops.Example: my @N = <STDIN>; That is a loop that builds a dynamically growing data structure for each line of input. Another example: my %hash = map { split( /=/, $_, $x + 1 ) } @v; Map is basically a short hand way of writing a foreach loop.

• When processing an input file (or stream from STDIN), to the extent possible, try to take a definitive action based upon the information contained in that line. Do something with that information ASAP. In general making a copy of a file's data in memory, only to process that data again line by line to extract information from that data structure is a bad idea. Please note the distinction between "data" and "information". "Information" is what you get when you process the "raw data".
• Don't save stuff in memory when it is not necessary to do so.