Merge pull request #9585 from MatthiasMuth/muthm-256

Challenge 256 Task 1 and 2 solutions in Perl by Matthias Muth

5 files changed, 234 insertions, 4 deletions

diff --git a/challenge-256/matthias-muth/README.md b/challenge-256/matthias-muth/README.md
index 970c56c8bd..e483f78d49 100644
--- a/challenge-256/matthias-muth/README.md
+++ b/challenge-256/matthias-muth/README.md
@@ -1,5 +1,127 @@
-**Challenge 244 solutions in Perl by Matthias Muth**
-<br/>
-(no blog post this time...)
+# Challenge 256 tasks: Easy Pairs - Easy Merge
+**Challenge 256 solutions in Perl by Matthias Muth**
+
+## Task 1: Maximum Pairs
+
+> You are given an array of distinct words, `@words`.<br/>
+> Write a script to find the maximum pairs in the given array. The words `$words[i]` and `$words[j]` can be a pair one is reverse of the other.<br/>
+> <br/>
+> Example 1<br/>
+> Input: @words = ("ab", "de", "ed", "bc")<br/>
+> Output: 1<br/>
+> There is one pair in the given array: "de" and "ed"<br/>
+> <br/>
+> Example 2<br/>
+> Input: @words = ("aa", "ba", "cd", "ed")<br/>
+> Output: 0<br/>
+> <br/>
+> Example 3<br/>
+> Input: @words = ("uv", "qp", "st", "vu", "mn", "pq"))<br/>
+> Output: 2<br/>
+
+Ah, an easy one.<br/>
+For each word we check whether we have seen its reverse before, and increment
+our counter if so. Then we remember that we have seen the current word.
+
+Perl supports us with the `reverse` function to reverse the characters of a string (also to reverse a list, but this is not what we use here).
+
+```perl
+#!/usr/bin/env perl
+use v5.36;
+
+sub maximum_pairs( @words ) {
+    my $n = 0;
+    my %known;
+    for ( @words ) {
+        ++$n if $known{ reverse $_ };
+        $known{$_} = 1;
+    }
+    return $n;
+}
+
+use Test2::V0 qw( -no_srand );
+is maximum_pairs( "ab", "de", "ed", "bc" ), 1,
+    'Example 1: maximum_pairs( ("ab", "de", "ed", "bc") ) == 1';
+is maximum_pairs( "aa", "ba", "cd", "ed" ), 0,
+    'Example 2: maximum_pairs( ("aa", "ba", "cd", "ed") ) == 0';
+is maximum_pairs( "uv", "qp", "st", "vu", "mn", "pq" ), 2,
+    'Example 3: maximum_pairs( ("uv", "qp", "st", "vu", "mn", "pq") ) == 2';
+done_testing;
+```
+
+If you don't have perl 5.36 (which I highly recommend!), you can use this
+instead: 
+
+```perl
+use v5.20;
+use warnings;
+use feature 'signatures';
+no warnings 'experimental::signatures';
+```
+Perl 5.20 has been around since 2014, so I guess that chances are high
+that your perl is more recent than that.<br/>
+If not, and you are not able to update your system's perl for any reason,
+I suggest installing [`perlbrew`](https://perlbrew.pl),
+which is an admin-free perl installation management tool.
+
+## Task 2: Merge Strings
+
+> You are given two strings, `$str1` and `$str2`.<br/>
+> Write a script to merge the given strings by adding in alternative order starting with the first string. If a string is longer than the other then append the remaining at the end.<br/>
+> <br/>
+> Example 1<br/>
+> Input: \$str1 = "abcd", \$str2 = "1234"<br/>
+> Output: "a1b2c3d4"<br/>
+> <br/>
+> Example 2<br/>
+> Input: \$str1 = "abc", \$str2 = "12345"<br/>
+> Output: "a1b2c345"<br/>
+> <br/>
+> Example 3<br/>
+> Input: \$str1 = "abcde", \$str2 = "123"<br/>
+> Output: "a1b2c3de"<br/>
+
+The idea for this challenge is to turn the two string into lists of characters,
+and then merge the two lists.<br/>
+There are a lot of functions for list manipulations in the `List::Util` core
+module, one of which is `mesh`. It does exactly what we need.
+The only downside is that if the lists are of different lengths, there will be
+`undef` values inserted in the result. But it is easy to `grep` those out
+before assembling the result into a return string.
+At least easier than splitting up the longer list into two parts, and after
+`mesh`ing the first part with the shorter string appending the second part.
+
+`mesh` has been part of `List::Util` since its version 1.56,
+which means has been part of standard Perl since Perl 5.25 (released in 2014).
+
+Its implementation is different from the `mesh` function in the
+`List::MoreUtils` CPAN module, in that it uses array references as parameters, not array variables that are used *by reference* (using prototypes).<br/>
+I prefer the `List::Util` version here,
+because we can directly use anonymous arrays containing the split characters as parameters,
+making it unnecessary to declare and use any array variables.
+
+```perl
+#!/usr/bin/env perl
+
+use v5.36;
+
+use List::Util qw( mesh );
+
+sub merge_strings( $str1, $str2 ) {
+    return join "",
+        grep defined,
+            mesh [ split //, $str1 ], [ split //, $str2 ];
+}
+
+use Test2::V0 qw( -no_srand );
+is merge_strings( "abcd", 1234 ), "a1b2c3d4",
+    'Example 1: merge_strings( ("abcd", 1234) ) == "a1b2c3d4"';
+is merge_strings( "abc", 12345 ), "a1b2c345",
+    'Example 2: merge_strings( ("abc", 12345) ) == "a1b2c345"';
+is merge_strings( "abcde", 123 ), "a1b2c3de",
+    'Example 3: merge_strings( ("abcde", 123) ) == "a1b2c3de"';
+done_testing;
+```
+
+#### **Thank you for the challenge!**
 
-**Thank you for the challenge!**
diff --git a/challenge-256/matthias-muth/blog.txt b/challenge-256/matthias-muth/blog.txt
new file mode 100644
index 0000000000..ee2ca51766
--- /dev/null
+++ b/challenge-256/matthias-muth/blog.txt
@@ -0,0 +1 @@
+https://github.com/MatthiasMuth/perlweeklychallenge-club/tree/muthm-256/challenge-256/matthias-muth#readme
diff --git a/challenge-256/matthias-muth/perl/ch-1.pl b/challenge-256/matthias-muth/perl/ch-1.pl
new file mode 100755
index 0000000000..88d640eb2d
--- /dev/null
+++ b/challenge-256/matthias-muth/perl/ch-1.pl
@@ -0,0 +1,30 @@
+#!/usr/bin/env perl
+#
+#       The Weekly Challenge - Perl & Raku
+#       (https://theweeklychallenge.org)
+#
+#       Challenge 256 Task 1: Maximum Pairs
+#
+#       Perl solution by Matthias Muth.
+#
+
+use v5.36;
+
+sub maximum_pairs( @words ) {
+    my $n = 0;
+    my %known;
+    for ( @words ) {
+        ++$n if $known{ reverse $_ };
+	$known{$_} = 1;
+    }
+    return $n;
+}
+
+use Test2::V0 qw( -no_srand );
+is maximum_pairs( "ab", "de", "ed", "bc" ), 1,
+    'Example 1: maximum_pairs( ("ab", "de", "ed", "bc") ) == 1';
+is maximum_pairs( "aa", "ba", "cd", "ed" ), 0,
+    'Example 2: maximum_pairs( ("aa", "ba", "cd", "ed") ) == 0';
+is maximum_pairs( "uv", "qp", "st", "vu", "mn", "pq" ), 2,
+    'Example 3: maximum_pairs( ("uv", "qp", "st", "vu", "mn", "pq") ) == 2';
+done_testing;
diff --git a/challenge-256/matthias-muth/perl/ch-2.pl b/challenge-256/matthias-muth/perl/ch-2.pl
new file mode 100755
index 0000000000..701aff3283
--- /dev/null
+++ b/challenge-256/matthias-muth/perl/ch-2.pl
@@ -0,0 +1,28 @@
+#!/usr/bin/env perl
+#
+#       The Weekly Challenge - Perl & Raku
+#       (https://theweeklychallenge.org)
+#
+#       Challenge 256 Task 2: Merge Strings
+#
+#       Perl solution by Matthias Muth.
+#
+
+use v5.36;
+
+use List::Util qw( mesh );
+
+sub merge_strings( $str1, $str2 ) {
+    return join "",
+	grep defined,
+	    mesh [ split //, $str1 ], [ split //, $str2 ];
+}
+
+use Test2::V0 qw( -no_srand );
+is merge_strings( "abcd", 1234 ), "a1b2c3d4",
+    'Example 1: merge_strings( ("abcd", 1234) ) == "a1b2c3d4"';
+is merge_strings( "abc", 12345 ), "a1b2c345",
+    'Example 2: merge_strings( ("abc", 12345) ) == "a1b2c345"';
+is merge_strings( "abcde", 123 ), "a1b2c3de",
+    'Example 3: merge_strings( ("abcde", 123) ) == "a1b2c3de"';
+done_testing;
diff --git a/challenge-256/matthias-muth/perl/challenge-256.txt b/challenge-256/matthias-muth/perl/challenge-256.txt
new file mode 100644
index 0000000000..2c68ed9512
--- /dev/null
+++ b/challenge-256/matthias-muth/perl/challenge-256.txt
@@ -0,0 +1,49 @@
+The Weekly Challenge - 256
+Monday, Feb 12, 2024
+
+
+Task 1: Maximum Pairs
+Submitted by: Mohammad Sajid Anwar
+
+You are given an array of distinct words, @words.
+Write a script to find the maximum pairs in the given array. The words $words[i] and $words[j] can be a pair one is reverse of the other.
+Example 1
+
+Input: @words = ("ab", "de", "ed", "bc")
+Output: 1
+
+There is one pair in the given array: "de" and "ed"
+
+Example 2
+
+Input: @words = ("aa", "ba", "cd", "ed")
+Output: 0
+
+Example 3
+
+Input: @words = ("uv", "qp", "st", "vu", "mn", "pq")
+Output: 2
+
+
+Task 2: Merge Strings
+Submitted by: Mohammad Sajid Anwar
+
+You are given two strings, $str1 and $str2.
+Write a script to merge the given strings by adding in alternative order starting with the first string. If a string is longer than the other then append the remaining at the end.
+Example 1
+
+Input: $str1 = "abcd", $str2 = "1234"
+Output: "a1b2c3d4"
+
+Example 2
+
+Input: $str1 = "abc", $str2 = "12345"
+Output: "a1b2c345"
+
+Example 3
+
+Input: $str1 = "abcde", $str2 = "123"
+Output: "a1b2c3de"
+
+
+Last date to submit the solution 23:59 (UK Time) Sunday 18th February 2024.