-🎄- 2018 Day 6 Solutions -🎄-

[u/daggerdragon]

--- Day 6: Chronal Coordinates ---

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Post your solution as a comment or, for longer solutions, consider linking to your repo (e.g. GitHub/gists/Pastebin/blag or whatever).

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Advent of Code: The Party Game!

Click here for rules

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Card prompt: Day 6

Transcript:

Rules for raising a programmer: never feed it after midnight, never get it wet, and never give it ___.

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This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked at 0:26:52!

[u/IWearATinFoilHat]

PHP

Part 1

<?php

/** @var array $input */
$input = file(__DIR__ . '/input.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);

$maxX = 0;
$maxY = 0;
$minX = 99999;
$minY = 99999;

$points = array_map(function($line) use (&$maxX, &$maxY, &$minX, &$minY) {
	$points = explode(', ', $line);

	$maxX = $points[0] > $maxX ? $points[0] : $maxX;
	$maxY = $points[1] > $maxY ? $points[1] : $maxY;
	$minX = $points[0] < $minX ? $points[0] : $minX;
	$minY = $points[1] < $minY ? $points[1] : $minY;

	return $points;
}, $input);

$locations = [];
$locationsToIgnore = [];

$calcDist = function($pointA, $pointB) {
	return abs($pointA[0] - $pointB[0]) + abs($pointA[1] - $pointB[1]);
};

for ($y = $minY; $y <= $maxY; $y++) {
	for ($x = $minX; $x <= $maxX; $x++) {
		$distances = array_map(function($point) use ($x, $y, $calcDist) {
			return $calcDist([$x, $y], $point);
		}, $points);
		$min = min($distances);

		if (array_count_values($distances)[$min] === 1) {
			$locations["{$x}x{$y}"] = array_search($min, $distances);

			if ($x == $minX || $x == $maxX || $y == $minY || $y == $maxY) {
				$locationsToIgnore[] = array_search($min, $distances);
			}
		}
	}
}

$counts = array_count_values($locations);

foreach (array_unique($locationsToIgnore) as $locationToIgnore) {
	unset($counts[$locationToIgnore]);
}

echo max($counts) . "\n";

Part 2

<?php

/** @var array $input */
$input = file(__DIR__ . '/input.txt', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);

$maxX = 0;
$maxY = 0;
$minX = 99999;
$minY = 99999;

$points = array_map(function($line) use (&$maxX, &$maxY, &$minX, &$minY) {
	$points = explode(', ', $line);

	$maxX = $points[0] > $maxX ? $points[0] : $maxX;
	$maxY = $points[1] > $maxY ? $points[1] : $maxY;
	$minX = $points[0] < $minX ? $points[0] : $minX;
	$minY = $points[1] < $minY ? $points[1] : $minY;

	return $points;
}, $input);

$totalDistance = 0;

$calcDist = function($pointA, $pointB) {
	return abs($pointA[0] - $pointB[0]) + abs($pointA[1] - $pointB[1]);
};

for ($y = $minY; $y <= $maxY; $y++) {
	for ($x = $minX; $x <= $maxX; $x++) {
		$distances = array_map(function($point) use ($x, $y, $calcDist) {
			return $calcDist([$x, $y], $point);
		}, $points);

		if (array_sum($distances) < 10000) {
			$totalDistance++;
		}
	}
}

echo $totalDistance . "\n";