97 lines
2.2 KiB
PHP
97 lines
2.2 KiB
PHP
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<?php
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function part1() {
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// Get elf instructions.
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$directions = file_get_contents('./2015/inputs/day3.txt');
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// Convert the string to an array for processing.
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$directions = str_split($directions);
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$position = [0,0];
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$deliveries = [];
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foreach ($directions as $direction) {
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// First, deliver a present at current location.
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$location_key = $position[0] . '_' . $position[1];
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$location_key = crypt($location_key, '123');
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if (isset($deliveries[$location_key])) {
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$deliveries[$location_key]++;
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}
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else {
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$deliveries[$location_key] = 1;
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}
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if ($direction == '^') {
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$position[1]++;
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}
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elseif($direction == 'v') {
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$position[1]--;
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}
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elseif ($direction == '>') {
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$position[0]++;
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}
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elseif ($direction == '<') {
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$position[0]--;
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}
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}
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return $deliveries;
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}
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function part2() {
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// Get elf instructions.
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$directions = file_get_contents('./2015/inputs/day3.txt');
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// Convert the string to an array for processing.
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$directions = str_split($directions);
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$santa_position = [0,0];
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$robo_position = [0,0];
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$deliveries = [];
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$turn = 'santa';
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foreach ($directions as $direction) {
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if ($turn == 'santa') {
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$deliveries = updateDeliveryList($deliveries, $santa_position);
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$santa_position = changeCoordinates($santa_position, $direction);
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$turn = 'robo';
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}
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elseif ($turn == 'robo') {
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$deliveries = updateDeliveryList($deliveries, $robo_position);
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$robo_position = changeCoordinates($robo_position, $direction);
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$turn = 'santa';
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}
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}
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return $deliveries;
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}
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function updateDeliveryList(array $list, $coords) {
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$location_key = $coords[0] . '_' . $coords[1];
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$location_key = crypt($location_key, '123');
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if (!isset($list[$location_key])) {
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$list[$location_key] = 1;
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}
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else {
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$list[$location_key]++;
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}
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return $list;
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}
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function changeCoordinates($coords, $move) {
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match ($move) {
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'^' => $coords[1]++,
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'v' => $coords[1]--,
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'>' => $coords[0]++,
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'<' => $coords[0]--,
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default => null,
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};
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return $coords;
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}
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function day3($part = 1) {
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if ($part == 1) {
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return count(part1());
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}
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elseif ($part == 2) {
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return count(part2());
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}
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}
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