39 lines
1.2 KiB
PHP
39 lines
1.2 KiB
PHP
<?php
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$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
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preg_match('#target area: x=(?P<x1>[\d-]*)..(?P<x2>[\d-]*), y=(?P<y2>[\d-]*)..(?P<y1>[\d-]*)#', $input[0], $found);
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$totalMaxY = 0;
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$velocities = 0;
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for ($x = 0; $x < 1500; $x++) {
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for ($y = -500; $y < 500; $y++) {
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$velocityX = $x;
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$velocityY = $y;
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$position = [0, 0];
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$maxY = 0;
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while ($position[0] < $found['x2'] && $position[1] > $found['y2']) {
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$position[0] += $velocityX;
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$position[1] += $velocityY;
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if ($velocityX != 0) {
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$velocityX += $velocityX > 0 ? -1 : 1;
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}
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if ($position[1] > $maxY) {
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$maxY = $position[1];
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}
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$velocityY--;
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if ($position[0] >= $found['x1'] &&
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$position[0] <= $found['x2'] &&
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$position[1] <= $found['y1'] &&
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$position[1] >= $found['y2']) {
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$velocities++;
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if ($maxY > $totalMaxY) {
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$totalMaxY = $maxY;
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}
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break;
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}
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}
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}
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}
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echo $velocities; //4556
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