#!/usr/bin/perl

$filename = "9.txt";

open(FILE, $filename);
@data = <FILE>;
close(FILE);

#Load input data into 2d array

for ($i = 0; $i < $#data + 1; $i++) {
    $line = $data[$i];
    $line =~ s/[^0-9]*//sgi;
    @horz = split("", $line);
    for ($z = 0; $z < $#horz + 1; $z++) {
        $cell[$z][$i] = $horz[$z];
    }
}


$xmax = $#horz + 1;
$ymax = $#data + 1;

$heightdata = 0;
$bcount = 0;
@points = ();

#For loop intentionally not indented in a normal way as this is a composite loop to iterate through the 2d array.

for ($b = 0; $b < $ymax; $b++) {
for ($a = 0; $a < $xmax; $a++) {


    # For all adjacent cells, load in their value. If adjacent to edge, treat it as a "9" cell.
    if (($a - 1) < 0) {
        $left = 9;
    }
    else
    {
        $left = $cell[$a - 1][$b];
    }
    if (($b - 1) < 0) {
        $top = 9;
    }
    else
    {
        $top = $cell[$a][$b - 1];
    }

    if (($a + 1) > ($xmax - 1)) {
        $right = 9;
    }
    else
    {
        $right = $cell[$a + 1][$b];
    }
    if (($b + 1) > ($ymax - 1)) {
        $bottom = 9;
    }
    else
    {
        $bottom = $cell[$a][$b + 1];
    }

    $current = $cell[$a][$b];

    if (($current < $left)&&($current < $right)&&($current < $top)&&($current < $bottom)) {
        #Found the lowest point of a "basin".
        $heightdata = $heightdata + $current + 1;
        $bcount++;
        push(@points, $a.",".$b);
    }

}
}

#Load in all "9" walls and all other as empty space.

for ($b = 0; $b < $ymax; $b++) {
for ($a = 0; $a < $xmax; $a++) {
    if ($cell[$a][$b] == 9) {
        $cell[$a][$b] = "111";
    }
    else
    {
        $cell[$a][$b] = "222";
    }
}
}


$freenumber = "333";

@basin = ();


#Give each lowest point a unique number starting from 333

foreach $p (@points) {
    ($x, $y) = split(",", $p);
    $cell[$x][$y] = $freenumber;
    $freenumber++;
}


$modified = 1;
$runcount = 0;


# VERY hacky "Paint bucket function" consisting of a while loop that runs forever until no more changes can be made.
while ($modified == 1) {
$modified = 0;

    for ($b = 0; $b < $ymax; $b++) {
    for ($a = 0; $a < $xmax; $a++) {

        #Same here, treat edge cells as having "111" walls.

        if (($a - 1) < 0) {
            $left = "111";
        }
        else
        {
            $left = $cell[$a - 1][$b];
        }
        if (($b - 1) < 0) {
            $top = "111";
        }
        else
        {
            $top = $cell[$a][$b - 1];
        }

        if (($a + 1) > ($xmax - 1)) {
            $right = "111";
        }
        else
        {
            $right = $cell[$a + 1][$b];
        }
        if (($b + 1) > ($ymax - 1)) {
            $bottom = "111";
        }
        else
        {
            $bottom = $cell[$a][$b + 1];
        }


        #If cell is empty, check if any adjacent cell is both non-wall and non-empty. Then overwrite value in cell with that value.
        if ($cell[$a][$b] eq "222") {
            unless (($left =~ m/(222|111)/)&&($right =~ m/(222|111)/)&&($top =~ m/(222|111)/)&&($bottom =~ m/(222|111)/)) {
                unless ($left =~ m/(222|111)/) {
                    $cell[$a][$b] = $left;
                    $modified = 1;
                }
                unless ($right =~ m/(222|111)/) {
                    $cell[$a][$b] = $right;
                    $modified = 1;
                }
                unless ($top =~ m/(222|111)/) {
                    $cell[$a][$b] = $top;
                    $modified = 1;
                }
                unless ($bottom =~ m/(222|111)/) {
                    $cell[$a][$b] = $bottom;
                    $modified = 1;
                }

            }
        }

    }
    }

    #Run whole thing backwards - makes the while loop like a hundred times faster.

    for ($b = ($ymax - 1); $b > -1; $b--) {
    for ($a = ($xmax - 1); $a > -1; $a--) {

        if (($a - 1) < 0) {
            $left = "111";
        }
        else
        {
            $left = $cell[$a - 1][$b];
        }
        if (($b - 1) < 0) {
            $top = "111";
        }
        else
        {
            $top = $cell[$a][$b - 1];
        }

        if (($a + 1) > ($xmax - 1)) {
            $right = "111";
        }
        else
        {
            $right = $cell[$a + 1][$b];
        }
        if (($b + 1) > ($ymax - 1)) {
            $bottom = "111";
        }
        else
        {
            $bottom = $cell[$a][$b + 1];
        }


        if ($cell[$a][$b] eq "222") {
            unless (($left =~ m/(222|111)/)&&($right =~ m/(222|111)/)&&($top =~ m/(222|111)/)&&($bottom =~ m/(222|111)/)) {
                unless ($left =~ m/(222|111)/) {
                    $cell[$a][$b] = $left;
                    $modified = 1;
                }
                unless ($right =~ m/(222|111)/) {
                    $cell[$a][$b] = $right;
                    $modified = 1;
                }
                unless ($top =~ m/(222|111)/) {
                    $cell[$a][$b] = $top;
                    $modified = 1;
                }
                unless ($bottom =~ m/(222|111)/) {
                    $cell[$a][$b] = $bottom;
                    $modified = 1;
                }

            }
        }

    }
    }

}

#Count number of basins using their unique number.

for ($b = 0; $b < $ymax; $b++) {
for ($a = 0; $a < $xmax; $a++) {
    $basin[$cell[$a][$b]]++;
}
}

$bigabasin = 0;
$bigbbasin = 0;
$bigcbasin = 0;

#Find 3 biggest basins:

for ($bascnt = 333; $bascnt < $freenumber; $bascnt++) {
    if ($basin[$bascnt] > $bigabasin) {
        $bigabasin = $basin[$bascnt];
    }
}
for ($bascnt = 333; $bascnt < $freenumber; $bascnt++) {
    if (($basin[$bascnt] > $bigbbasin)&&($basin[$bascnt] < $bigabasin)) {
        $bigbbasin = $basin[$bascnt];
    }
}
for ($bascnt = 333; $bascnt < $freenumber; $bascnt++) {
    if (($basin[$bascnt] > $bigcbasin)&&($basin[$bascnt] < $bigbbasin)) {
        $bigcbasin = $basin[$bascnt];
    }
}

#Print results.

print "\n";
print $heightdata."\n";
print $bcount."\n";
print $freenumber."\n";
print $bigabasin . "--" . $bigbbasin . "--" . $bigcbasin . "--" . ($bigabasin * $bigbbasin * $bigcbasin) . "\n";