AOC 2024 12-1

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php
3 months ago
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<body style="margin-left: 10px; font-family: consolas; font-size: 18px">

<?php
$day = 12;
$file = "advent$day.txt";
echo "-- Start processing $file --<br><br>";

$input = file_get_contents($file);
$rowArray = explode("\r\n", $input);

$plotArray = array();
$regionArray = array();
$regionList = array();

for ($i = 0; $i < count($rowArray); $i ++) {

    $plotArray[$i] = str_split($rowArray[$i]);
}

$dirArray = [
    "N",
    "E",
    "S",
    "W"
];

$objectArray = array();
$rowCount = count($plotArray);
$colCount = count($plotArray[0]);
$offset = $colCount;
$resultCount = 0;

$i = 0;
for ($row = 0; $row < $rowCount; $row ++) {

    for ($col = 0; $col < $colCount; $col ++) {

        $object = new stdClass();
        $object->id = $i;
        $object->row = $row;
        $object->col = $col;
        $object->value = $plotArray[$row][$col];
        $object->region = false;
        $object->borders = false;
        
        $objectArray[] = $object;
        
        $i++;
    }
}

function paint($region) {

    global $objectArray;
    global $offset;
    global $toPaint;

    $id = array_pop($toPaint);
    
    $nEdge = true;
    $eEdge = false;
    $sEdge = false;
    $wEdge = false;
    
    $borders = 0;
    
    if (isset($objectArray[$id-$offset])) $nEdge = false;
    if ($id % $offset == $offset-1) $eEdge = true;
    if (!isset($objectArray[$id+$offset])) $sEdge = true;
    if ($id % $offset == 0) $wEdge = true;
   
    $me =  $objectArray[$id]->value;
    
    if (!$nEdge) {        
        $north =  $objectArray[$id-$offset]->value;
        $nPainted = $objectArray[$id-$offset]->region;
        
        if ($me == $north && !$nPainted) array_push($toPaint, $id-$offset); 
        if ($me != $north) $borders++; 
        
    } else $borders++; // edge

    if (!$eEdge) {
        $east = $objectArray[$id+1]->value;
        $ePainted = $objectArray[$id+1]->region;
        
        if ($me == $east && !$ePainted) array_push($toPaint, $id+1);
        if ($me != $east) $borders++;
        
    } else $borders++; // edge
    
    if (!$sEdge) {
        $south = $objectArray[$id+$offset]->value;
        $sPainted = $objectArray[$id+$offset]->region;
        
        if ($me == $south && !$sPainted) array_push($toPaint, $id+$offset);
        if ($me != $south) $borders++;
        
    } else $borders++; // edge
    
    if (!$wEdge) {
        $west = $objectArray[$id-1]->value;
        $wPainted = $objectArray[$id-1]->region;
        
        if ($me == $west && !$wPainted) array_push($toPaint, $id-1);
        if ($me != $west) $borders++;
        
    } else $borders++; // edge
    
// start at ID - set region to 0

    $objectArray[$id]->region = $region;
    $objectArray[$id]->borders = $borders;


}

//for ($i = 0; $i < count($objectArray); $i++) {
        
//}

function findObject($row, $col){
    global $objectArray;
    
    foreach ($objectArray as $element) {
        if ($col == $element->col && $row == $element->row) {
            return $element;
        }
    }
    
    return false;
}

function findNoRegion(){
    global $objectArray;
    
    foreach ($objectArray as $element) {
        if ($element->region === false) {
            return $element->id;
        }
    }
    
    return false;
}

$done = false;

// regions have index 1

$region = 1;

while (!$done) {
    
// find first unpainted

    $noRegion = findNoRegion();
    if ($noRegion === false) $done = true;
    
    else {

// paint it and its neighbours with first region...

$toPaint = [$noRegion];
while (count($toPaint) > 0) {
    
    paint($region);
    
}

    }

// stop when all are painted same region

// increase region

$region++;

// find first unpainted...

// stop when none are unpainted

}

foreach ($objectArray as $object) {

    $region = $object->region;
    
    $regionArray[$region][] = $object->borders;
}

for ($i = 1; $i < count($regionArray)+1; $i++) {
    
    $plotCount = count($regionArray[$i]);

    $borderSum = array_sum($regionArray[$i]);
    
    echo "Region $i<br>";
    
    echo "Plots = $plotCount<br>";
    echo "Perimeter = $borderSum<br><br>";
 
    $resultCount = $resultCount + ($plotCount * $borderSum);
    
}

echo "Result Count = $resultCount<br>";

echo "<br><br>-- Finished processing $file --<br>";
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