day06: Solve puzzles

Makefile

@@ -18,6 +18,8 @@ day05:
 	php day05/solve.php input
 
 day06:
+	php day06/solve.php input
+
 day07:
 day08:
 day09:

day06/example.txt

@@ -0,0 +1 @@
+3,4,3,1,2

day06/input.txt

@@ -0,0 +1 @@
+2,1,1,4,4,1,3,4,2,4,2,1,1,4,3,5,1,1,5,1,1,5,4,5,4,1,5,1,3,1,4,2,3,2,1,2,5,5,2,3,1,2,3,3,1,4,3,1,1,1,1,5,2,1,1,1,5,3,3,2,1,4,1,1,1,3,1,1,5,5,1,4,4,4,4,5,1,5,1,1,5,5,2,2,5,4,1,5,4,1,4,1,1,1,1,5,3,2,4,1,1,1,4,4,1,2,1,1,5,2,1,1,1,4,4,4,4,3,3,1,1,5,1,5,2,1,4,1,2,4,4,4,4,2,2,2,4,4,4,2,1,5,5,2,1,1,1,4,4,1,4,2,3,3,3,3,3,5,4,1,5,1,4,5,5,1,1,1,4,1,2,4,4,1,2,3,3,3,3,5,1,4,2,5,5,2,1,1,1,1,3,3,1,1,2,3,2,5,4,2,1,1,2,2,2,1,3,1,5,4,1,1,5,3,3,2,2,3,1,1,1,1,2,4,2,2,5,1,2,4,2,1,1,3,2,5,5,3,1,3,3,1,4,1,1,5,5,1,5,4,1,1,1,1,2,3,3,1,2,3,1,5,1,3,1,1,3,1,1,1,1,1,1,5,1,1,5,5,2,1,1,5,2,4,5,5,1,1,5,1,5,5,1,1,3,3,1,1,3,1

day06/lib.php

@@ -0,0 +1,33 @@
+<?php
+declare(strict_types=1);
+
+function buildFishIndex(array $fishes) : array
+{
+    $index = [];
+
+    foreach ($fishes as $val) {
+        $index[$val] = ($index[$val] ?? 0) + 1;
+    }
+
+    return $index;
+}
+
+function decreaseFishesIndex(array $fishIndex) : array
+{
+    $newIndex = [];
+
+    foreach ($fishIndex as $days => $amount) {
+        $newIndex[intval($days - 1)] = intval($amount);
+    }
+
+    foreach ($newIndex as $day => $amount) {
+        if ($day < 0) {
+            unset($newIndex[$day]);
+
+            $newIndex[8] = $amount;
+            $newIndex[6] = ($newIndex[6] ?? 0) + $amount;
+        }
+    }
+
+    return $newIndex;
+}

day06/solve.php

@@ -0,0 +1,39 @@
+<?php
+declare(strict_types=1);
+
+require_once(__DIR__.'/../lib/functions.php');
+require_once(__DIR__.'/lib.php');
+
+$entries = getLines(__DIR__.'/'.$argv[1].'.txt');
+
+timedPrintf(
+    '[2021-12-06.1] Amount of fishes after 80 days: %d [Time: %ss]',
+    (function (array $entries) : int {
+        $fishes = explode(',', $entries[0]);
+
+        $fishIndex = buildFishIndex($fishes);
+
+        for ($i = 1; $i <= 80; $i++) {
+            $fishIndex = decreaseFishesIndex($fishIndex);
+        }
+
+        return array_sum($fishIndex);
+    }),
+    $entries
+);
+
+timedPrintf(
+    '[2021-12-06.2] Amount of fishes after 256 days: %d [Time: %ss]',
+    (function (array $entries) : int {
+        $fishes = explode(',', $entries[0]);
+
+        $fishIndex = buildFishIndex($fishes);
+
+        for ($i = 1; $i <= 256; $i++) {
+            $fishIndex = decreaseFishesIndex($fishIndex);
+        }
+
+        return array_sum($fishIndex);
+    }),
+    $entries
+);