add perl solution for wk-100 ch-2

1 files changed, 40 insertions, 0 deletions

diff --git a/challenge-100/alexander-pankoff/perl/ch-2.pl b/challenge-100/alexander-pankoff/perl/ch-2.pl
new file mode 100755
index 0000000000..4027ecf9a8
--- /dev/null
+++ b/challenge-100/alexander-pankoff/perl/ch-2.pl
@@ -0,0 +1,40 @@
+#!/usr/bin/env perl
+use v5.20;
+use utf8;
+use strict;
+use warnings;
+use feature qw(say signatures);
+no warnings 'experimental::signatures';
+
+use List::Util qw(min);
+
+{
+    test_triangle_sum();
+}
+
+sub test_triangle_sum() {
+
+    my @test_cases = (
+        [ [ [1], [ 2, 4 ], [ 6, 4, 9 ], [ 5, 1, 7, 2 ] ], 8 ],
+        [ [ [3], [ 3, 1 ], [ 5, 2, 3 ], [ 4, 3, 1, 3 ] ], 7 ]
+    );
+
+    require Test::More;
+    Test::More->import( tests => scalar @test_cases );
+
+    for my $test (@test_cases) {
+        my ( $triangle, $expected_sum ) = @{$test};
+        ok(
+            triangle_sum($triangle) == $expected_sum,
+            "The minimum path is $expected_sum"
+        );
+    }
+}
+
+sub triangle_sum ( $triangle, $pos = 0 ) {
+    my ( $cur, @rest ) = @$triangle;
+    return 0 if !$cur;
+
+    return $cur->[$pos] +
+      min( triangle_sum( \@rest, $pos ), triangle_sum( \@rest, $pos + 1 ), );
+}