112 lines
2.4 KiB
PHP
112 lines
2.4 KiB
PHP
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<?php
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// prepare numbers and grids
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$parts = explode("\n\n", file_get_contents('./input.txt'));
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$numbers = array_map('intval', explode(',', array_shift($parts)));
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$grids = array_map(static function($part) { return explode("\n", $part); }, $parts);
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array_walk_recursive($grids, static function (&$grid) {
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if (is_string($grid)) {
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$grid = array_map(static function($g) {
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return 0;
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}, array_flip(array_map('trim', str_split($grid, 3))));
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}
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});
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/**
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* Marks cell as done
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*
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* @param array $grids
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* @param int $number
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*/
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function modify_grids(array &$grids, int $number)
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{
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foreach ($grids as $i_grid => $grid) {
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foreach ($grid as $i_row => $row) {
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foreach ($row as $cell => $cell_val) {
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if ($cell === $number) {
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$grids[$i_grid][$i_row][$cell] = 1;
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}
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}
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}
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}
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}
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/**
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* List all unmarked cell from a grid
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*
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* @param array $grid
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*
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* @return array
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*/
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function get_unmarked_from(array $grid): array
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{
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$unmarked = [];
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foreach ($grid as $row) {
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$unmarked = array_merge($unmarked, array_keys(array_filter($row, static function($cell) {
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return $cell === 0;
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})));
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}
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return $unmarked;
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}
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/**
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* Check if a grid is winning
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*
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* @param array $grids
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*
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* @return bool|array
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*/
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function check_grids(array $grids): bool|array
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{
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foreach ($grids as $grid) {
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if (check_lines($grid)) {
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return get_unmarked_from($grid);
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}
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$rotated_grid = [];
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$i = 0;
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while (!empty($grid)) {
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foreach ($grid as $j => $row) {
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$rotated_grid[$i][array_key_last($row)] = array_pop($row);
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$grid[$j] = $row;
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if (empty($row)) unset($grid[$j]);
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}
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$i++;
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}
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if (check_lines($rotated_grid)) {
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return get_unmarked_from($rotated_grid);
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}
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}
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return false;
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}
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/**
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* Check if a line is all done
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*
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* @param array $grid
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*
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* @return bool|array
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*/
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function check_lines(array $grid): bool|array
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{
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foreach ($grid as $row) {
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if (array_sum($row) === 5) {
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return true;
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}
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}
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return false;
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}
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foreach ($numbers as $number) {
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modify_grids($grids, (int)$number);
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$grid = check_grids($grids);
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if ($grid !== false) {
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echo array_sum($grid) * $number;
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break;
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}
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}
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