41 lines
1.1 KiB
PHP
41 lines
1.1 KiB
PHP
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<?php
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$input_file = '../inputs/day3.txt';
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if (file_exists($input_file)) {
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$input = file_get_contents($input_file);
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if ($input != null) {
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$coordinates = explode("\n", $input);
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print 'Part 1 answer: ' . solve_part_one($coordinates) . "\n";
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print 'Part 2 answer: ' . solve_part_two($coordinates) . "\n";
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}
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}
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function solve_part_one(array $coords): int
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{
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return solve_for_slope($coords, 3, 1);
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}
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function solve_part_two(array $coords): int
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{
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return solve_for_slope($coords, 1, 1)
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* solve_for_slope($coords, 3, 1)
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* solve_for_slope($coords, 5, 1)
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* solve_for_slope($coords, 7, 1)
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* solve_for_slope($coords, 1, 2);
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}
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function solve_for_slope(array $coords, int $incr_x, int $incr_y): int
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{
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$current_coords = ['x' => 0, 'y' => 0];
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$trees = 0;
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while ($current_coords['y'] < (count($coords) - 1)) {
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$current_coords['x'] += $incr_x;
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$current_coords['y'] += $incr_y;
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$current_line = trim($coords[$current_coords['y']]);
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$actual_x = $current_coords['x'] % strlen($current_line);
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if ($current_line[$actual_x] === '#')
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$trees += 1;
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}
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return $trees;
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}
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