From dd6293e6c7c4752f20974bb223deeb8c1c8b8373 Mon Sep 17 00:00:00 2001
From: Mohammad S Anwar <mohammad.anwar@yahoo.com>
Date: Mon, 9 Sep 2019 01:23:00 +0100
Subject: - Added solutions by Colin Crain.

---
 challenge-024/colin-crain/perl5/ch-1.pl |  1 +
 challenge-024/colin-crain/perl5/ch-2.pl | 98 +++++++++++++++++++++++++++++++++
 2 files changed, 99 insertions(+)
 create mode 100644 challenge-024/colin-crain/perl5/ch-1.pl
 create mode 100644 challenge-024/colin-crain/perl5/ch-2.pl

diff --git a/challenge-024/colin-crain/perl5/ch-1.pl b/challenge-024/colin-crain/perl5/ch-1.pl
new file mode 100644
index 0000000000..da1d2f1a0c
--- /dev/null
+++ b/challenge-024/colin-crain/perl5/ch-1.pl
@@ -0,0 +1 @@
+perl -e “”
diff --git a/challenge-024/colin-crain/perl5/ch-2.pl b/challenge-024/colin-crain/perl5/ch-2.pl
new file mode 100644
index 0000000000..cd4701ed12
--- /dev/null
+++ b/challenge-024/colin-crain/perl5/ch-2.pl
@@ -0,0 +1,98 @@
+#! /opt/local/bin/perl
+#
+#       inverted_index.pl
+#
+#
+#
+#       2019 colin crain
+## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ## ##
+
+use warnings;
+use strict;
+use feature ":5.26";
+
+## ## ## ## ## MAIN
+
+my @docs = @ARGV;
+
+say "enter search terms: ";
+my @TEST_TERMS = split /\s/, <STDIN>;
+
+my $idx = make_index( @docs );
+
+my ($match, $all) = search_index($idx, @TEST_TERMS);
+
+say "matched all:\n", (join ", ", $match->@*);
+say "by prevalence:\n", (join "\n ", $all->@*);
+
+
+## ## ## ## ## SUBS
+
+sub make_index {
+    my @documents = @_;
+
+    my $idx = {};
+
+    ## open and slurp down the file,
+    ## split on whitespace to make a word list
+    for my $file ( @documents ) {
+        open (my $fh, "<" , $file) or die "can't open $file to read: $!\n";
+        my @words = split /\s/, <$fh>;
+        close $fh;
+
+        ## run it through a unique filter
+        my @unique_words = uniq( @words );
+
+        ## add each word to the index adding the file to the value array
+        for my $word ( @unique_words ) {
+            if (exists $idx->{$word}) {
+                push $idx->{$word}->@*, $file;
+            }
+            else {
+                $idx->{$word} = [$file];
+            }
+        }
+    }
+
+    return $idx;
+}
+
+sub search_index {
+## takes an index hashref and a list of search terms
+## returns two lists, the first of docs with all terms
+## the second a sorted list of documents by term prevalence
+## ( most words found first, will include all documents with at least one word)
+    my ($idx, @words) = @_;
+
+    ## for each search term, add its index doc list to the result
+    my @result;
+    for my $search_term ( @words ) {
+        if (exists $idx->{$search_term}) {
+            push @result, $idx->{$search_term}->@*;
+        }
+    }
+
+    ## count the document occurrences in the concatenated index lists
+    my %result_count;
+    foreach my $document ( @result ) {
+        $result_count{$document}++;
+    }
+    my @unique_result = uniq( @result );
+
+    ## if the occurence count equals the search term count, all terms match to the document
+    my @all_terms = grep { $result_count{$_} == scalar @words } @unique_result;
+
+    ## alternately, sort the unique result list on prevalence
+    my @by_prevalence = sort { $result_count{$b} <=> $result_count{$a} } @unique_result;
+
+    return (\@all_terms, \@by_prevalence);
+}
+
+sub uniq {
+## filters a list for unique terms, with first occurence preserved
+## we could grab List::Util::uniq but here we roll our own with the "seen" trick
+    my %seen;
+    return grep { ! $seen{$_}++ } @_;
+}
+
+
-- 
cgit