Week 206 Task 1

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+#!/usr/bin/env perl
+# vim:set ts=4 sw=4 sts=4 et ai wm=0 nu:
+#=============================================================================
+# ch-1.pl Perl Weekly Challenge Week 206 Task 1 Shortest Time
+#=============================================================================
+# Copyright (c) 2023, Bob Lied
+#=============================================================================
+# You are given a list of time points, at least 2, in the 24-hour clock format
+# HH:MM. Write a script to find out the shortest time in minutes between any
+# two time points.
+# Example 1 Input: @time = ("00:00", "23:55", "20:00") Output: 5
+#   Since the difference between "00:00" and "23:55" is the shortest
+# Example 2 Input: @array = ("01:01", "00:50", "00:57") Output: 4
+# Example 3 Input: @array = ("10:10", "09:30", "09:00", "09:55") Output: 15
+##
+# Example 1 implies that 00:00 can represent midnight either at the start
+# of the day, or at the end of the day.  Ambiguous if 24:00 is allowed.
+#
+# All the interesting times involve midnight.  If all the
+# points were within the same day, then a pair like 00:10, 23:50 would be
+# 23 hours and 40 minutes long.  But if we allow wrapping around midnight,
+# there's only 20 minutes between them.  The problem specification is
+# ambiguously silent, except that example with 00:00 kind of implies that
+# we should wrap around.
+#=============================================================================
+
+use v5.36;
+
+use List::Util qw/min/;
+
+use constant  {
+    MINPERDAY => 24 * 60
+};
+
+use Getopt::Long;
+my $Verbose = 0;
+my $DoTest  = 0;
+
+GetOptions("test" => \$DoTest, "verbose" => \$Verbose);
+exit(!runTest()) if $DoTest;
+
+# Map a string in HH:MM format to the minute past midnight.
+sub hhmmToMin($hhmm)
+{
+    my ($hour, $min) = split(':', $hhmm);
+    my $minOfDay = $hour * 60 + $min;
+    return ($minOfDay == MINPERDAY ? 0 : $minOfDay);
+}
+
+sub shortestTime($moments)
+{
+    my @minutes =  map { hhmmToMin($_) } $moments->@*;
+
+    my $least = MINPERDAY;
+
+    # Do a full NxN scan of every possible pair.  Getting the difference
+    # in either direction will wash away the ambiguity of 00:00.
+    for ( my $beg = 0 ; $beg <= $#minutes ; $beg++ )
+    {
+        for ( my $end = 0; $end <= $#minutes ; $end++ )
+        {
+            next if $end == $beg;
+            my $d1 = ( $minutes[$end] - $minutes[$beg] ) % MINPERDAY;
+            $least = min($least, $d1 );
+        }
+    }
+    return $least;
+}
+
+sub runTest
+{
+    use Test2::V0;
+
+    is( shortestTime( [ "00:00", "23:55", "20:00" ] ),           5, "Example 1");
+    is( shortestTime( [ "01:01", "00:50", "00:57" ] ),           4, "Example 2");
+    is( shortestTime( [ "10:10", "09:30", "09:00", "09:55" ] ), 15, "Example 3");
+
+    is( shortestTime( [ "00:02", "23:58", "00:57" ] ),           4, "'round midnight");
+    is( shortestTime( [ "00:02", "00:57", "00:02" ] ),           0, "Zero");
+    is( shortestTime( [ "23:55", "24:00", "00:02" ] ),           2, "24:00");
+    is( shortestTime( [ "23:55", "24:00", "00:07" ] ),           5, "24:00 again");
+
+    done_testing;
+}
+