TWC294

Challenge Link

Task1

We count the number of consecutive elements according to this algorithm. (We can also use a simple Perl hash instead of the Set::Scalar module):

#!/usr/bin/env perl
use strict;
use warnings;
use List::Util qw(max);
use Set::Scalar;

sub consecutive_sequence{
  my ($arr) = @_;
  my $s = Set::Scalar->new(@$arr);
  my $res = 0;
  foreach my $i(0..$#$arr){
    unless($s->has($arr->[$i]-1)){
      my $j = $arr->[$i];
      $j++ while($s->has($j));
      $res = max($res,$j - $arr->[$i])
    }
  }
  $res == 1 ? -1 : $res
}

printf "%d\n",consecutive_sequence([10,4,20,1,3,2]);
printf "%d\n",consecutive_sequence([0,6,1,8,5,2,4,3,0,7]);
printf "%d\n",consecutive_sequence([10,30,20]);

Task2

We find the next permutation of the array according to this algorithm.

#!/usr/bin/env perl
use strict;
use warnings;

sub next_permutation{
  my ($arr) = @_;
  my $p = -1;
  for(my $i = $#$arr-1; $i >= 0; --$i){
    do{$p = $i; last}if($arr->[$i] < $arr->[$i+1])
  }
  return reverse @$arr if $p == -1;
  for(my $i = $#$arr; $i >= $p+1; --$i){
    if($arr->[$i] > $arr->[$p]){
      ($arr->[$i],$arr->[$p]) = ($arr->[$p],$arr->[$i]);
      last
    }
  }
  @$arr
}

printf "(%s)\n",join ', ',next_permutation([1,2,3]);
printf "(%s)\n",join ', ',next_permutation([2,1,3]);
printf "(%s)\n",join ', ',next_permutation([3,1,2]);