12th day both parts

12/part1.php

@@ -0,0 +1,29 @@
+<?php
+$input = file('input', FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+$input = array_map(fn($line) => explode('-', $line), $input);
+
+$adjacencyList = [];
+foreach ($input as $key => $item) {
+    if ($item[1] != 'start') $adjacencyList[$item[0]][] = $item[1];
+    if ($item[0] != 'start') $adjacencyList[$item[1]][] = $item[0];
+}
+$history = [];
+echo track($adjacencyList, "start", $history);
+function track($adjacencyList, $cave, $history) {
+    $count = 0;
+    $history[] = $cave;
+    foreach($adjacencyList[$cave] as $path) {
+        if(strtolower($path) === $path && in_array($path,$history)) {
+            //bad path, go no further
+        }
+        else if($path == "end") {
+            $count += 1;
+            echo implode(",",$history) ."\n";
+        }
+        else {
+            $count += track($adjacencyList, $path, $history);
+        }
+    }
+    return $count;
+}
+