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|
#!/usr/bin//perl
use strict;
use warnings;
use List::Util qw(any);
sub remove_numbers {
my $numbers = shift;
my $to_rem = shift;
foreach my $n (keys %$to_rem) {
delete $numbers->{$n};
}
}
sub numbers_in_row {
my $field = shift;
my $row = shift;
my $numbers = {};
for(my $i=0; $i<9; $i++) {
my $number = $field->[9*$row + $i];
$numbers->{$number} = 1 if $number;
}
return $numbers;
}
sub numbers_in_col {
my $field = shift;
my $col = shift;
my $numbers = {};
for(my $i=0; $i<9; $i++) {
my $number = $field->[9*$i + $col];
$numbers->{$number} = 1 if $number;
}
return $numbers;
}
sub numbers_in_block {
my $field = shift;
my $block = shift;
my $numbers = {};
my $blk_row = int($block / 3);
my $blk_col = $block % 3;
for(my $row=0; $row<3; $row++) {
for (my $col=0; $col<3; $col++) {
my $number = $field->[9*(3*$blk_row + $row) + (3*$blk_col + $col)];
$numbers->{$number} = 1 if $number;
}
}
return $numbers;
}
sub collect_numbers {
my $field = shift;
my $row_n = [];
my $col_n = [];
my $blk_n = [];
for(my $i=0; $i<9; $i++) {
$row_n->[$i] = numbers_in_row($field, $i);
}
for(my $i=0; $i<9; $i++) {
$col_n->[$i] = numbers_in_col($field, $i);
}
for(my $i=0; $i<9; $i++) {
$blk_n->[$i] = numbers_in_block($field, $i);
}
return ($row_n, $col_n, $blk_n);
}
sub print_field {
my $field = shift || return;
for(my $i=0; $i<9; $i++) {
for(my $j=0; $j<9; $j++) {
print $field->[9*$i + $j] . " ";
}
print "\n";
}
print "\n";
}
sub find_candidates {
my $field = shift;
my ($row_n, $col_n, $blk_n) = collect_numbers($field);
restart:
my $candidates = {};
for(my $row=0; $row<9; $row++) {
for(my $col=0; $col<9; $col++) {
next if $field->[9*$row + $col];
my $blk = 3*int($row / 3) + int($col / 3);
my %numbers = map { $_ => 1 } 1..9;
remove_numbers(\%numbers, $row_n->[$row]);
remove_numbers(\%numbers, $col_n->[$col]);
remove_numbers(\%numbers, $blk_n->[$blk]);
if (scalar keys %numbers == 1) {
# there is only one possibility -> restart search with updated field
my $n = (keys %numbers)[0];
$field->[9*$row + $col] = $n;
$row_n->[$row]->{$n} = 1;
$col_n->[$col]->{$n} = 1;
$blk_n->[$blk]->{$n} = 1;
goto restart;
} elsif (scalar keys %numbers > 1) {
$candidates->{9*$row + $col} = [ sort keys %numbers ];
} else {
# no candidate possible on this position
return;
}
}
}
return $candidates;
}
sub solve {
my @field = @_;
my $candidates = find_candidates(\@field) || return;
if (scalar keys %$candidates == 0) {
return \@field;
}
my @field_copy = @field;
# iterate remaining positions with multiple possibilities
foreach my $pos (sort { scalar @{$candidates->{$a}} <=> scalar @{$candidates->{$b}} } keys %$candidates) {
@field = @field_copy;
foreach my $cand (@{$candidates->{$pos}}) {
@field[$pos] = $cand;
my $solved_field = solve(@field);
return $solved_field if $solved_field;
}
return;
}
}
sub main {
my $content;
open FILE, "<096.txt" or die "Can't open file: $!\n";
while(<FILE>) {
$content .= $_;
}
close FILE;
my @sudokus = split('\n?Grid [0-9]+\n', $content);
shift @sudokus; # remove empty first element
my $sum = 0;
foreach my $sudoku (@sudokus) {
my @field = split("\n?", $sudoku);
my $solution = solve(@field);
$sum += 100*$solution->[0] + 10*$solution->[1] + 1*$solution->[2] . "\n";
}
print $sum . "\n";
}
main();
|
