[2018-12-01] Add second challange samples and solution

day1/main.php

@@ -12,6 +12,30 @@ function puzzle1(array $changes) : int
     return $frequency;
 }
 
+function puzzle2(array $changes) : int
+{
+    $frequency = 0;
+
+    // Start building the frequency history with the current one
+    $history = [
+        $frequency => 1,
+    ];
+
+    while (true) {
+        foreach ($changes as $change) {
+            $frequency += $change;
+
+            $history[$frequency]++;
+
+            if ($history[$frequency] == 2) {
+                return $frequency;
+            }
+        }
+    }
+
+    return $frequency;
+}
+
 echo 'First challange samples:'.PHP_EOL;
 echo puzzle1(['+1','+1','+1']).PHP_EOL;              // 3
 echo puzzle1(['+1','+1','-2']).PHP_EOL;              // 0
@@ -19,3 +43,13 @@ echo puzzle1(['-1','-2','-3']).PHP_EOL;              // -6
 
 echo 'First challange solution:'.PHP_EOL;
 echo puzzle1(explode(PHP_EOL, trim(file_get_contents(dirname(__FILE__).'/input.txt')))).PHP_EOL.PHP_EOL;
+
+
+echo 'Second challange samples:'.PHP_EOL;
+echo puzzle2(['+1','-1']).PHP_EOL;                   // 0
+echo puzzle2(['+3','+3','+4','-2','-4']).PHP_EOL;    // 10
+echo puzzle2(['-6','+3','+8','+5','-6']).PHP_EOL;    // 5
+echo puzzle2(['+7','+7','-2','-7','-4']).PHP_EOL;    // 14
+
+echo 'Second challange solution:'.PHP_EOL;
+echo puzzle2(explode(PHP_EOL, trim(file_get_contents(dirname(__FILE__).'/input.txt')))).PHP_EOL.PHP_EOL;