From cfdd866c80d181a8f3f0e68bc6fdbfcd5e8a5732 Mon Sep 17 00:00:00 2001
From: Fung Cheok Yin <61836418+E7-87-83@users.noreply.github.com>
Date: Sun, 8 Mar 2020 23:59:32 +0800
Subject: Create ch-1.pl

---
 challenge-050/cheok-yin-fung/perl/ch-1.pl | 71 +++++++++++++++++++++++++++++++
 1 file changed, 71 insertions(+)
 create mode 100644 challenge-050/cheok-yin-fung/perl/ch-1.pl

diff --git a/challenge-050/cheok-yin-fung/perl/ch-1.pl b/challenge-050/cheok-yin-fung/perl/ch-1.pl
new file mode 100644
index 0000000000..e7c3294ba5
--- /dev/null
+++ b/challenge-050/cheok-yin-fung/perl/ch-1.pl
@@ -0,0 +1,71 @@
+#!/usr/bin/perl
+use strict;
+use warnings;
+
+# Caution: The following codes work for distinct interval heads only. 
+
+my @L = (0) x 100;
+$L[100] = 1;
+$L[101] = -1;
+my %interval;     # key: the head of the interval; value: the tail of the interval
+
+sub newroute {
+	for my $i ($_[0]..$_[1]) {$L[$i]++;}
+	$interval{$_[0]}=$_[1];
+}
+
+
+
+newroute(2,7);
+newroute(3,9);
+newroute(10,12);
+newroute(15,19);
+newroute(18,22);
+
+newroute(100,100); # a temporary arrangement
+my @trainstation = sort {$a <=> $b} keys %interval;
+
+my %finterval;  # key: the head of the interval; value: the tail of the interval
+
+
+my $stationnum = 0;
+
+
+
+sub seektermination {
+	my $i = $_[0];
+	my $nextstop = $_[1];
+	while ($L[$i] > 0 and $i < $nextstop) {
+		$i++;
+	}
+
+	if ($L[$i] == 0 and $i<$nextstop) {
+		return $i-1;
+	}
+	if ($L[$i]>1) {
+		$stationnum++; 
+		return seektermination($_[0], $trainstation[$stationnum+1]);
+	}
+	if ($i==$nextstop and $L[$i-1] == 1 and $L[$i]==1) {
+		return $i-1;
+	}
+}
+
+
+
+
+
+
+while ($stationnum<=$#trainstation-1) {
+	my $start = $trainstation[$stationnum];
+	$finterval{$start} = seektermination($start, $trainstation[$stationnum+1]);
+	$stationnum++;
+}
+
+
+delete $finterval{100}; #goodbye to the temporary arrangement
+foreach my $s (sort {$a <=> $b} keys %finterval) {
+	print "[", $s, ", ", $finterval{$s}, "]", "\n";  
+}
+
+
-- 
cgit