14th day both parts

14/part1.php

@@ -0,0 +1,22 @@
+<?php
+$input    = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+$template = array_shift($input);
+$pairs    = [];
+foreach ($input as $item) {
+    $line = explode(' -> ', $item);
+    $pairs[$line[0]] = $line[1];
+}
+
+
+$newTemplate = $template;
+for ($j = 0; $j < 10; $j++) {
+    $tmpTemplate = $newTemplate;
+    for ($i = 0; $i < strlen($tmpTemplate) - 1; $i++) {
+        $window      = substr($tmpTemplate, $i, 2);
+        $newTemplate = substr_replace($newTemplate, $pairs[$window], $i + 1 + $i, 0);
+    }
+}
+$characters = array_count_values(str_split(($newTemplate)));
+sort($characters);
+echo array_pop($characters) - array_shift($characters); //2549
+