2022 Day 5 part 1

2022/day5.php

@@ -0,0 +1,37 @@
+<?php
+
+$input = explode("\n", file_get_contents('day5.input'));
+
+$empty = array_search('', $input, true);
+
+$stackDescriptions = array_slice($input, 0, $empty - 1);
+$commands = array_slice($input, $empty + 1);
+
+
+$numbers = array_filter(explode(' ', $input[$empty - 1]));
+
+$stacks = [];
+foreach($numbers as $number) {
+    $stacks[$number] = [];
+}
+
+foreach ($stackDescriptions as $line) {
+    $items = array_map(fn ($str) => trim($str, '[] '), str_split($line, 4));
+    $crates = array_combine($numbers, $items);
+    foreach ($crates as $stack => $crate) {
+        if ($crate !== '') {
+            array_unshift($stacks[$stack], $crate);
+        }
+    }
+}
+
+foreach ($commands as $command) {
+    preg_match('/move (\d+) from (\d+) to (\d+)/', $command, $matches);
+    [$x, $count, $from, $to] = $matches;
+    for ($i = 0; $i < $count; $i++) {
+        array_push($stacks[$to], array_pop($stacks[$from]));
+    }
+}
+
+$result = implode('', array_map('end', $stacks));
+echo 'Top crates: ' . $result;