TWC284

Challenge Link

Task1

We look for the number which has a frequency equal to its value:

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

sub lucky_integer{
  my %h;
  $h{$_}++ foreach @{$_[0]};
  max map{$h{$_} == $_ ? $_ : -1} keys %h
}

printf "%d\n",lucky_integer([2,2,3,4]);
printf "%d\n",lucky_integer([1,2,2,3,3,3]);
printf "%d\n",lucky_integer([1,1,1,3]);

Task2

We sort the elements according to their order in the second list:

#!/usr/bin/env perl
use strict;
use warnings;
use Data::Show;

sub relative_sort{
  my (%ranks,%ranked);
  $ranks{$_[1]->[$_]} = $_ foreach 0..$#{$_[1]};
  $ranked{$_} = defined $ranks{$_} ? 1 : 0 foreach @{$_[0]};
  sort{
    ($ranked{$b} <=> $ranked{$a}) ||
      ($ranks{$a} || 0) <=> ($ranks{$b} || 0) ||
      $a <=> $b
  } @{$_[0]}
}

print show relative_sort([2,3,9,3,1,4,6,7,2,8,5],[2,1,4,3,5,6]);
print show relative_sort([3,3,4,6,2,4,2,1,3],[1,3,2]);
print show relative_sort([3,0,5,0,2,1,4,1,1],[1,0,3,2]);