✨ Finit le jour 3

day_3/part_1.php

@@ -0,0 +1,15 @@
+<?php
+
+$rucksacks = explode("\n", file_get_contents('./input.txt'));
+
+$lettersToNumbers = array_merge(range('a', 'z'), range('A', 'Z'));
+
+echo array_sum(
+    array_map(
+        static function($rucksack) use ($lettersToNumbers) {
+            [$f, $s] = array_map('str_split', str_split($rucksack, strlen($rucksack)/2));
+            return array_search(current(array_intersect($f, $s)), $lettersToNumbers, true) + 1;
+        },
+        $rucksacks
+    )
+);

day_3/part_2.php

@@ -0,0 +1,17 @@
+<?php
+
+$rucksacks = explode("\n", file_get_contents('./input.txt'));
+
+$lettersToNumbers = array_merge(range('a', 'z'), range('A', 'Z'));
+
+$groups = array_chunk($rucksacks, 3);
+
+echo array_sum(
+    array_map(
+        static function($rucksacks) use ($lettersToNumbers) {
+            [$f, $s, $t] = array_map('str_split', $rucksacks);
+            return array_search(current(array_intersect($f, $s, $t)), $lettersToNumbers, true) + 1;
+        },
+        $groups
+    )
+);