Move solutions out of the source itself

data/Y21/day3/Day3.php

@@ -0,0 +1,39 @@
+<?php
+
+namespace trizz\AdventOfCode\Y21;
+
+use trizz\AdventOfCode\Solution;
+
+final class Day3 extends Solution
+{
+    public static null|int|string $part1ExampleResult = 198;
+
+    public static null|int|string $part1Result = 3_309_596;
+
+    #[\Override]
+    public function part1(array $data): int
+    {
+        $bits = [];
+
+        foreach ($data as $binary) {
+            $split = str_split($binary);
+
+            foreach ($split as $position => $value) {
+                $bits[$position][] = $value;
+            }
+        }
+
+        $gammaRate = '';
+        $epsilonRate = '';
+
+        foreach ($bits as $bit) {
+            $zeros = array_filter($bit, static fn ($value): bool => $value === '0');
+            $ones = array_filter($bit, static fn ($value): bool => $value === '1');
+
+            $gammaRate .= ($ones > $zeros) ? '1' : '0';
+            $epsilonRate .= ($ones < $zeros) ? '1' : '0';
+        }
+
+        return (int) (bindec($gammaRate) * bindec($epsilonRate));
+    }
+}