day03: Solve puzzles

Makefile

@@ -9,6 +9,8 @@ day02:
 	php day02/solve.php input
 
 day03:
+	php day03/solve.php input
+
 day04:
 day05:
 day06:

day03/example.txt

@@ -0,0 +1,12 @@
+00100
+11110
+10110
+10111
+10101
+01111
+00111
+11100
+10000
+11001
+00010
+01010

day03/solve.php

@@ -0,0 +1,70 @@
+<?php
+declare(strict_types=1);
+
+require_once(__DIR__.'/../lib/functions.php');
+
+$entries = getLines(__DIR__.'/'.$argv[1].'.txt');
+
+timedPrintf(
+    '[2021-12-03.1] Resulting power consumption: %d [Time: %ss]',
+    (function (array $entries) : int {
+        // Fill array with zeroes
+        $counters = array_fill(0, strlen($entries[0]), 0);
+
+        foreach ($entries as $entry) {
+            for ($i = 0; $i < strlen($entry); $i++) {
+                if ($entry[$i] === '1') {
+                    $counters[$i] += 1;
+                }
+            }
+        }
+
+        $gamma = '';
+        $epsilon = '';
+        foreach ($counters as $counter) {
+            $gamma .= ($counter > (count($entries) / 2)) ? '1' : '0';
+            $epsilon .= ($counter > (count($entries) / 2)) ? '0' : '1';
+        }
+
+        return bindec($gamma) * bindec($epsilon);
+    }),
+    $entries
+);
+
+timedPrintf(
+    '[2021-12-03.2] Resulting life support rating: %d [Time: %ss]',
+    (function (array $entries) : int {
+        $fn = function (array $numbers, int $column, bool $filterByMore, callable $fn) : int {
+            $counter = 0;
+
+            foreach ($numbers as $number) {
+                if ($number[$column] === '1') {
+                    $counter++;
+                }
+            }
+
+            $filterByNumber = $filterByMore ?
+                (($counter >= (count($numbers) / 2)) ? '1' : '0') :
+                (($counter <  (count($numbers) / 2)) ? '1' : '0');
+
+            // Filter the array
+            $numbers = array_filter($numbers, function (string $number) use ($column, $filterByNumber) : bool {
+                return $number[$column] === $filterByNumber;
+            });
+
+            // If only one number left, decode it from binary and return it
+            if (count($numbers) === 1) {
+                return bindec(array_shift($numbers));
+            }
+
+            // Otherwise, recurse more
+            return $fn($numbers, $column + 1, $filterByMore, $fn);
+        };
+
+        $o2generator = $fn($entries, 0, true, $fn);
+        $co2 = $fn($entries, 0, false, $fn);
+
+        return $o2generator * $co2;
+    }),
+    $entries
+);