add solution week 79 task 2

1 files changed, 44 insertions, 0 deletions

diff --git a/challenge-079/steven-wilson/perl/ch-2.pl b/challenge-079/steven-wilson/perl/ch-2.pl
new file mode 100644
index 0000000000..58b775bfe8
--- /dev/null
+++ b/challenge-079/steven-wilson/perl/ch-2.pl
@@ -0,0 +1,44 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+use feature qw/ say /;
+use List::Util qw/ sum max /;
+use Test::More;
+
+my @N1_t = ( 2, 1, 4, 1, 2, 5 );
+my @N2_t = ( 3, 1, 3, 1, 1, 5 );
+ok( water_trapped( \@N1_t ) == 6 );
+ok( water_trapped( \@N2_t ) == 6 );
+done_testing();
+
+sub water_trapped {
+    my $input_ref   = shift;
+    my @input       = @{$input_ref};
+    my $hist_width  = scalar @input;
+    my $hist_height = max(@input);
+    my $total_water_trapped;
+
+    for my $row ( 2 .. $hist_height ) {
+        my @row_array;
+        for my $column ( 0 .. $hist_width - 1 ) {
+            if ( $input[$column] >= $row ) {
+                $row_array[$column] = 0;
+            }
+            else {
+                $row_array[$column] = 1;
+            }
+        }
+        if ( !( sum(@row_array) == $hist_width - 1 ) ) {
+            while ( $row_array[0] == 1 ) {
+                shift @row_array;
+            }
+            while ( $row_array[-1] == 1 ) {
+                pop @row_array;
+            }
+            $total_water_trapped += sum(@row_array);
+        }
+    }
+    return $total_water_trapped;
+}
+