[2017-12-06] Solutions for both puzzles

Makefile

@@ -16,6 +16,8 @@ day5:
 	php day5/main.php
 
 day6:
+	php day6/main.php
+
 day7:
 day8:
 day9:

day6/main.php

@@ -0,0 +1,93 @@
+<?php
+// https://adventofcode.com/2017/day/6
+
+function puzzle1(string $input) : int
+{
+    $history = [];
+    $banks = explode("\t", $input);
+    $sum = 0;
+
+    while (true) {
+        // Copy banks, sort it, get biggest number out
+        $copy = $banks;
+        rsort($copy);
+        $biggestNumber = array_shift($copy);
+
+        // Find the key and value to distribute
+        $distributeKey = array_search($biggestNumber, $banks);
+        $distributeValue = $banks[$distributeKey];
+        $banks[$distributeKey] = 0;
+
+        while ($distributeValue > 0) {
+            $distributeKey++;
+
+            if ($distributeKey > count($banks) - 1) {
+                $distributeKey = 0;
+            }
+
+            $banks[$distributeKey]++;
+
+            $distributeValue--;
+        }
+
+        // Increment reallocations
+        $sum++;
+
+        // Check history if we had this state before
+        $index = implode($banks, '');
+
+        if (isset($history[$index])) {
+            break;
+        }
+
+        $history[$index] = true;
+    }
+
+    return $sum;
+}
+
+function puzzle2(string $input) : int
+{
+    $history = [];
+    $banks = explode("\t", $input);
+    $sum = 0;
+
+    while (true) {
+        // Copy banks, sort it, get biggest number out
+        $copy = $banks;
+        rsort($copy);
+        $biggestNumber = array_shift($copy);
+
+        // Find the key and value to distribute
+        $distributeKey = array_search($biggestNumber, $banks);
+        $distributeValue = $banks[$distributeKey];
+        $banks[$distributeKey] = 0;
+
+        while ($distributeValue > 0) {
+            $distributeKey++;
+
+            if ($distributeKey > count($banks) - 1) {
+                $distributeKey = 0;
+            }
+
+            $banks[$distributeKey]++;
+
+            $distributeValue--;
+        }
+
+        // Increment reallocations
+        $sum++;
+
+        // Check history if we had this state before
+        $index = implode($banks, '');
+
+        if (isset($history[$index])) {
+            $sum = $sum - $history[$index];
+            break;
+        }
+
+        $history[$index] = $sum;
+    }
+
+    return $sum;
+}