TL;DR

Here we are with TASK #1 from The Weekly Challenge #202. Enjoy!

The challenge

You are given an array of integers.

Write a script to print 1 if there are THREE consecutive odds in the given array otherwise print 0.

Example 1

Input: @array = (1,5,3,6)
Output: 1

Example 2

Input: @array = (2,6,3,5)
Output: 0

Example 3

Input: @array = (1,2,3,4)
Output: 0

Example 4

Input: @array = (2,3,5,7)
Output: 1

The questions

Wow, is this ambiguous!

Suppose that you’re the proud owner of five paintings by Vincent van Gogh. Wow.

Then someone comes and asks you: Hey! Do you have three paintings by Vincent van Gogh?!?.

Sure, you do have them (you have more, actually), but chances are that your answer will be Why… no! I have five!.

So I guess that my questions is… can we allow for any other odd in the array? Can they appear consecutive to the first three ones?

The solution

OK, let’s take into consideration a couple options, in Raku:

#!/usr/bin/env raku
use v6;
sub MAIN (*@args) {
   my ($n-streaks, $longest-streak) = consecutive-odds(@args);

   # strict
   $*ERR.put('(one single streak of exactly three odds, no other odd)');
   $*OUT.put(($n-streaks == 1 && $longest-streak == 3) ?? 1 !! 0);

   # lax
   $*ERR.put('at least three odds in a row');
   $*OUT.put(($longest-streak >= 3) ?? 1 !! 0);
}

sub consecutive-odds (@array) {
   my $longest-streak = 0;
   my $current-streak = 0;
   my $n-streaks = 0;
   for @array -> $item {
      if $item %% 2 {
         ++$n-streaks if $current-streak;
         $current-streak = 0;
      }
      else {
         ++$current-streak;
         ++$longest-streak if $longest-streak < $current-streak;
      }
   }
   ++$n-streaks if $current-streak;
   return $n-streaks, $longest-streak;
}

And the obvious Perl translation:

#!/usr/bin/env perl
use v5.24;
use warnings;
use experimental 'signatures';
no warnings 'experimental::signatures';

my ($n_streaks, $longest_streak) = consecutive_odds(@ARGV);

# strict
say {*STDERR} '(one single streak of exactly three odds, no other odd)';
say {*STDOUT} $n_streaks == 1 && $longest_streak == 3 ? 1 : 0;

# lax
say {*STDERR} 'at least three odds in a row';
say {*STDOUT} $longest_streak >= 3 ? 1 : 0;

sub consecutive_odds (@array) {
   my $longest_streak = 0;
   my $current_streak = 0;
   my $n_streaks = 0;
   for my $item (@array) {
      if ($item % 2) {
         ++$current_streak;
         ++$longest_streak if $longest_streak < $current_streak;
      }
      else {
         ++$n_streaks if $current_streak;
         $current_streak = 0;
      }
   }
   ++$n_streaks if $current_streak;
   return ($n_streaks, $longest_streak);
}

In both cases, we’re collecting some statistics about the @array, so that we can take our decision at a later time. The explanation for the result is printed on standard error, so that standard output only gets 0 or 1.

And that’s all, folks!