From 8596ec41a913700b55cfbaa0e9f993e7d008305c Mon Sep 17 00:00:00 2001
From: wanderdoc <wanderdoc@googlemail.com>
Date: Sun, 5 Sep 2021 15:50:46 +0200
Subject: Solution to task#2 challenge-128

---
 challenge-128/wanderdoc/perl/ch-2.pl | 125 +++++++++++++++++++++++++++++++++++
 1 file changed, 125 insertions(+)
 create mode 100644 challenge-128/wanderdoc/perl/ch-2.pl

diff --git a/challenge-128/wanderdoc/perl/ch-2.pl b/challenge-128/wanderdoc/perl/ch-2.pl
new file mode 100644
index 0000000000..4f38dcf760
--- /dev/null
+++ b/challenge-128/wanderdoc/perl/ch-2.pl
@@ -0,0 +1,125 @@
+#!perl
+use strict;
+use warnings FATAL => qw(all);
+
+=prompt
+You are given two arrays of arrival and departure times of trains at a railway station. Write a script to find out the minimum number of platforms needed so that no train needs to wait.
+Example 1:
+Input: @arrivals   = (11:20, 14:30)
+       @departutes = (11:50, 15:00)
+Output: 1
+    The 1st arrival of train is at 11:20 and this is the only train at the station, so you need 1 platform.
+    Before the second arrival at 14:30, the first train left the station at 11:50, so you still need only 1 platform.
+
+Example 2:
+Input: @arrivals   = (10:20, 11:00, 11:10, 12:20, 16:20, 19:00)
+       @departutes = (10:30, 13:20, 12:40, 12:50, 20:20, 21:20)
+Output: 3
+    Between 11:00 and 12:20, there would be at least 3 trains at the station, so we need minimum 3 platforms.
+=cut
+
+use Time::Piece;
+use Time::Seconds;
+
+use List::MoreUtils qw(pairwise);
+use List::Util qw(min max);
+
+sub platforms
+{
+     my ($arr, $dep) = @_;
+     my $max = 0;
+     my $min = ONE_DAY;
+
+     for ($arr, $dep)
+     {
+          @$_ = map { 
+               my $t1 = Time::Piece->strptime($_, "%H:%M"); 
+               $t1->epoch;} @$_;
+     }
+
+
+     my @pairs = pairwise { $a > $b ? [$a, $b + ONE_DAY] : [$a, $b] } 
+               @$arr, @$dep; 
+     for my $pair ( @pairs )
+     {
+          $min = min($min, @$pair);
+          $max = max($max, @$pair);
+     }
+
+
+     my %platforms; 
+     my %output;
+     for my $ts ( $min .. $max )
+     {
+          for my $pair ( @pairs )
+          {
+               next if ($ts < $pair->[0] or $ts > $pair->[1]);
+               push @{$output{ ++$platforms{$ts} }}, $ts;
+
+          }
+     }
+     print "1 platform is enough.$/" if max(keys %output == 1);
+     for my $platform ( grep $_ > 1, sort {$b <=> $a} keys %output) 
+     {
+          my @intervals = _num2arr( @{$output{$platform}});
+          print "At least ${platform} platforms at", ': ';
+          print join(', ',map join(' - ', map _sec2hm($_), $_->[0], $_->[1]), @intervals), $/;
+
+     }
+}
+
+print "Example 1 (modified):$/";
+my @arrivals   = qw (11:20 14:30 14:59);
+my @departutes = qw (11:50 15:00 00:01);
+platforms(\@arrivals, \@departutes);
+
+
+print "Example 2:$/";
+@arrivals   = qw(10:20 11:00 11:10 12:20 16:20 19:00);
+@departutes = qw(10:30 13:20 12:40 12:50 20:20 21:20);
+platforms(\@arrivals, \@departutes);
+
+
+
+
+
+sub _num2arr
+{
+     my @numbers = sort { $a <=> $b} @_;
+     my @output;
+     my $previous = $numbers[0];
+     my $from = my $to = $previous;
+     my $last;
+
+
+     for my $num ( @numbers[1 .. $#numbers] )
+     {
+          if ( 1 >= ($num - $previous) )
+          {
+               $previous = $num;
+          }
+          else
+          {
+
+
+               my $to = $previous;
+               push @output, [$from, $to];
+               $previous = $num;
+               $from = $to = $previous;
+          }
+          $last = $num;
+     }
+     push @output, [$from, $last];
+
+     return @output;
+}
+
+
+sub _sec2hm
+{
+     my $seconds = $_[0];
+     $seconds -= ONE_DAY if $seconds > ONE_DAY;
+     return join(':',
+          sprintf("%02d",int($seconds / ONE_HOUR)),
+          sprintf("%02d",int(($seconds % ONE_HOUR) / ONE_MINUTE)));
+}
\ No newline at end of file
-- 
cgit