50 lines
1.3 KiB
PHP
50 lines
1.3 KiB
PHP
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<?php
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$input = file_get_contents('./input.txt');
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preg_match('/^target area: x=(\d+)\.\.(\d+), y=(-?\d+)\.\.(-?\d+)$/', $input, $matches);
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[, $x_min, $x_max, $y_min, $y_max] = $matches;
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$target = ['x_min' => $x_min, 'x_max' => $x_max, 'y_min' => $y_min, 'y_max' => $y_max];
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function increment(&$x, &$y, &$x_velocity, &$y_velocity)
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{
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$x += $x_velocity;
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$y += $y_velocity;
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if ($x_velocity > 0) $x_velocity -= 1;
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elseif ($x_velocity < 0) $x_velocity += 1;
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else $x_velocity = 0;
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$y_velocity -= 1;
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}
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function check($x, $y, $target)
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{
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return $x >= $target['x_min'] &&
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$x <= $target['x_max'] &&
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$y >= $target['y_min'] &&
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$y <= $target['y_max'];
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}
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$possibilities = [];
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for ($i = 0; $i <= abs($target['x_max']); $i++) {
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for ($j = -abs($target['y_min']); $j <= abs($target['y_min']); $j++) {
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if ($i === 0 && $j === 0) continue;
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$x = 0;
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$y = 0;
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$x_velocity = $i;
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$y_velocity = $j;
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while(!check($x, $y, $target)) {
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echo sprintf('x: %s, y: %s%s', $x, $y, "\n");
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increment($x, $y, $x_velocity, $y_velocity);
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if ($y <= $target['y_min']) {
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break;
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}
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}
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if (check($x, $y, $target)) {
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$possibilities[] = sprintf('%s,%s', $i, $j);
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}
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}
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}
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echo count($possibilities);
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