71 lines
1.8 KiB
PHP
71 lines
1.8 KiB
PHP
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<?php
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$instructions = explode("\n", file_get_contents('input.txt'));
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const NORTH = 'N';
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const SOUTH = 'S';
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const EAST = 'E';
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const WEST = 'W';
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const LEFT = 'L';
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const RIGHT = 'R';
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const FORWARD = 'F';
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$facings = [NORTH, EAST, SOUTH, WEST];
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$facing = EAST;
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$east = 0;
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$north = 0;
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function doingInstruction($direction, $value)
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{
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global $north, $east, $facings, $facing;
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switch ($direction) {
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case NORTH:
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$north += $value;
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break;
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case SOUTH:
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$north -= $value;
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break;
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case EAST:
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$east += $value;
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break;
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case WEST:
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$east -= $value;
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break;
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case LEFT:
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$turns = $value / 90;
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$array_position = array_search($facing, $facings);
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$array_max = 4;
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for ($i = $turns; $i > 0; $i--) {
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$array_position--;
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if ($array_position === -1) {
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$array_position = $array_max - 1;
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}
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}
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$facing = $facings[$array_position];
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break;
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case RIGHT:
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$turns = $value / 90;
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$array_position = array_search($facing, $facings);
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$array_max = 4;
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for ($i = 0; $i < $turns; $i++) {
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$array_position++;
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if ($array_position === $array_max) {
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$array_position = 0;
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}
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}
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$facing = $facings[$array_position];
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break;
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case FORWARD:
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doingInstruction($facing, (int)$value);
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break;
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}
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}
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foreach ($instructions as $instruction) {
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$direction = $instruction[0];
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$value = (int)substr($instruction, 1);
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doingInstruction($direction, $value);
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}
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echo abs($east) + abs($north);
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