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|
#!/usr/bin/env perl
use v5.20;
use utf8;
use strict;
use warnings;
use autodie;
use feature qw(say signatures);
no warnings 'experimental::signatures';
use List::Util qw(
all
any
max
min
);
# You are given m x n character matrix consists of O and X only.
#
# Write a script to count the total number of X surrounded by O only. Print 0 if none found.
my ($file) = @ARGV;
my $fh;
if ($file) {
open( $fh, '<', $file );
}
else {
$fh = *STDIN;
}
my $matrix = parse_input($fh);
my @lonely_xses = lonely_xses($matrix);
say scalar @lonely_xses;
if ( $ENV{DEBUG} ) {
say "Lonely X found at Row "
. ( $_->[0] + 1 ) . ' Col '
. ( $_->[1] + 1 ) . '.'
for @lonely_xses;
}
exit 0;
sub lonely_xses($matrix) {
return grep {
all { $matrix->[ $_->[0] ][ $_->[1] ] eq 'O' } neighbors( $matrix, $_ );
} x_positions($matrix);
}
sub x_positions($matrix) {
return
grep { $matrix->[ $_->[0] ][ $_->[1] ] eq 'X' }
combinations( [ 0 .. $#{$matrix} ], [ 0 .. $#{ $matrix->[0] } ] );
}
sub neighbors ( $matrix, $pos ) {
my ( $row, $col ) = @$pos;
my @neighbor_rows =
( max( 0, $row - 1 ) .. min( $row + 1, $#{$matrix} ) );
my @neighbor_cols =
( max( 0, $col - 1 ) .. min( $col + 1, $#{ $matrix->[0] } ) );
grep { $_->[0] != $row || $_->[1] != $col }
combinations( \@neighbor_rows, \@neighbor_cols );
}
sub combinations ( $a, $b ) {
map {
my $x = $_;
map { [ $x, $_ ] } @$b;
} @$a;
}
sub parse_input($fh) {
chomp( my @lines = <$fh> );
my $length;
my @rows = map {
my $line = $_;
return () if $line !~ m/\S/;
$line =~ m/^\s*\[\s*(.*?)\s*\]\s*$/;
die "cannot parse $line" unless $1;
my @os_and_xses = split( /\s+/, $1 );
die "invalid input in $line" if any { $_ ne 'O' && $_ ne 'X' } @os_and_xses;
$length //= @os_and_xses;
die "column count not uniform" unless @os_and_xses == $length;
\@os_and_xses;
} @lines;
return \@rows;
}
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