hsegnitz
diff --git a/‎php/2023/15/01.php
Lines changed: 65 additions & 0 deletions b/‎php/2023/15/01.php
Lines changed: 65 additions & 0 deletions
diff --git a/‎php/2023/15/example.txt
73 Bytes b/‎php/2023/15/example.txt
73 Bytes
diff --git a/‎php/2023/15/input.txt
22.4 KB b/‎php/2023/15/input.txt
22.4 KB
@@ -0,0 +1,65 @@
+<?php
+
+namespace Year2023\Day15;
+
+$start = microtime(true);
+
+#$in = file_get_contents('example.txt');
+$in = file_get_contents('input.txt');
+
+$commands = explode(",", $in);
+
+$boxes = array_fill(0, 256, []);
+
+$part1Sum = 0;
+foreach ($commands as $command) {
+    $part1Sum += hash($command);
+
+    if (preg_match('/(\w+)([=-])(\d*)/', $command, $out)) {
+        [,$label, $operation, $focalLength] = $out;
+    } else {
+        die('no match');
+    }
+
+    $boxNumber = hash($label);
+
+    if ($operation === '-') {
+        if (isset($boxes[$boxNumber][$label])) {
+            unset($boxes[$boxNumber][$label]);
+        }
+    } elseif ($operation === '=') {
+        $boxes[$boxNumber][$label] = $focalLength;
+    }
+}
+
+$part2Sum = 0;
+foreach ($boxes as $boxNum => $box) {
+    foreach (array_values($box) as $lensNum => $focalLength) {
+        $part2Sum += ($boxNum+1) * ($lensNum+1) * $focalLength;
+    }
+}
+
+
+
+
+
+echo "\n", $part1Sum, "\n";
+echo "\n", $part2Sum, "\n";
+
+
+echo microtime(true) - $start;
+echo "\n";
+
+
+function hash(string $command): int
+{
+    $val = 0;
+    for ($i = 0, $iMax = strlen($command); $i < $iMax; $i++) {
+        $val += ord($command[$i]);
+        $val *= 17;
+        $val %= 256;
+    }
+
+    return $val;
+}
+