day 3 part 2

Author: dannyvankooten

2024-php/01.php

@@ -36,5 +36,5 @@
 echo "--- Day 1: Historian Hysteria ---", PHP_EOL;
 echo "Part 1: ", $pt1, PHP_EOL;
 echo "Part 2: ", $pt2, PHP_EOL;
-echo "Took ", microtime(true) - $time_start, " seconds", PHP_EOL;
+echo "Took ", (microtime(true) - $time_start) * 1000, " ms", PHP_EOL;
 echo PHP_EOL;

2024-php/02.php

@@ -51,5 +51,5 @@ function is_safe(array $numbers): bool
 echo "--- Day 2: Red-Nosed Reports ---", PHP_EOL;
 echo "Part 1: ", $pt1, PHP_EOL;
 echo "Part 2: ", $pt2, PHP_EOL;
-echo "Took ", microtime(true) - $time_start, " seconds", PHP_EOL;
+echo "Took ", (microtime(true) - $time_start) * 1000, " ms", PHP_EOL;
 echo PHP_EOL;

2024-php/03.php

@@ -1,13 +1,40 @@
 <?php
-
+$time_start = microtime(true);
 $input = trim(file_get_contents('03.txt'));
 
-$matches = [];
-preg_match_all('/mul\((\d{1,3}),(\d{1,3})\)/', $input, $matches);
+function op($in): int
+{
+	$matches = [];
+	preg_match_all('/mul\((\d{1,3}),(\d{1,3})\)/', $in, $matches);
+	$out = 0;
+	for ($i = 0; $i < count($matches[0]); $i++) {
+		$out += (int) $matches[1][$i] * (int) $matches[2][$i];
+	}
+	return $out;
+}
+
+$pt1 = op($input);
 
-$pt1 = 0;
-for ($i = 0; $i < count($matches[0]); $i++) {
-	$pt1 += $matches[1][$i] * $matches[2][$i];
+// for part 2, we use the same regex but first do some string manipulation
+while (true) {
+	$pos = strpos($input, "don't()");
+	if ($pos === false) {
+		break;
+	}
+
+	$new = substr($input, 0, $pos);
+
+	$next = strpos($input, "do()", $pos+1);
+	if ($next !== false) {
+		$new .= substr($input, $next);
+	}
+	$input = $new;
 }
 
-echo "Part 1: " , $pt1, PHP_EOL;
+$pt2 = op($input);
+
+echo "--- Day 3: Mull It Over ---", PHP_EOL;
+echo "Part 1: ", $pt1, PHP_EOL;
+echo "Part 2: ", $pt2, PHP_EOL;
+echo "Took ", (microtime(true) - $time_start) * 1000, " ms", PHP_EOL;
+echo PHP_EOL;