[2017-12-05] Solutions for both puzzles

Makefile

@@ -13,6 +13,8 @@ day4:
 	php day4/main.php
 
 day5:
+	php day5/main.php
+
 day6:
 day7:
 day8:

day5/main.php

@@ -0,0 +1,52 @@
+<?php
+// https://adventofcode.com/2017/day/5
+
+function puzzle1(string $input)
+{
+    $jumps = 0;
+    $placement = 0;
+    $instructions = array_filter(explode(PHP_EOL, $input));
+
+    while (true) {
+        // Get current jump size
+        $jumpSize = $instructions[$placement];
+
+        // Increment jump size
+        $instructions[$placement]++;
+
+        // Do jump
+        $placement += $jumpSize;
+        $jumps++;
+
+        if ($placement >= count($instructions)) {
+            return $jumps;
+        }
+    }
+}
+
+function puzzle2(string $input)
+{
+    $jumps = 0;
+    $placement = 0;
+    $instructions = array_filter(explode(PHP_EOL, $input));
+
+    while (true) {
+        // Get current jump size
+        $jumpSize = $instructions[$placement];
+
+        // Update instructions
+        if ($instructions[$placement] >= 3) {
+            $instructions[$placement]--;
+        } else {
+            $instructions[$placement]++;
+        }
+
+        // Do jump
+        $placement += $jumpSize;
+        $jumps++;
+
+        if ($placement >= count($instructions)) {
+            return $jumps;
+        }
+    }
+}