day 15 pt 1

jthatch · jthatch · commit a27e95fa8889 · 2021-10-25T21:50:45.000+01:00
diff --git a/README.md b/README.md
@@ -4,7 +4,7 @@ The solutions to [advent of code 2020](https://adventofcode.com/2020), solved us
 ### Solutions 🥳🎉
 > 🎄 [Day 1](/src/Day1.php) 🎅 [Day 2](/src/Day2.php) ☃️ [Day 3](/src/Day3.php) 🦌 [Day 4](/src/Day4.php) 🍪 [Day 5](/src/Day5.php) 
 > 🥛 [Day 6](/src/Day6.php) 🧦 [Day 7](/src/Day7.php) 🎁 [Day 8](/src/Day8.php)   
-> ⛄ [Day 9](/src/Day9.php) 🛐 [Day 10](/src/Day10.php) ⛄ [Day 11](/src/Day11.php) 🍪 [Day 12](/src/Day12.php) ☃️ [Day 13](/src/Day13.php) 🎅 [Day 14](/src/Day14.php) 
+> ⛄ [Day 9](/src/Day9.php) 🛐 [Day 10](/src/Day10.php) ⛄ [Day 11](/src/Day11.php) 🍪 [Day 12](/src/Day12.php) ☃️ [Day 13](/src/Day13.php) 🎅 [Day 14](/src/Day14.php) 🎄 [Day 15](/src/Day15.php) 
 
 ### About
 My attempts at tacking the awesome challenges at [Advent of Code 2020](https://adventofcode.com/2020/day/1) using PHP8.
diff --git a/input/day15.txt b/input/day15.txt
@@ -0,0 +1 @@
+14,3,1,0,9,5
diff --git a/src/Day14.php b/src/Day14.php
@@ -71,16 +71,6 @@ public function solvePart2(): int|string|null
                 }
                 // now our memory position in binary ($posBin) contains a number of floating values (X)
                 // these can be either 0 or 1 giving us 2^X possible memory combinations.
-
-                // Example: given a $posBin like 000000000000000000000000000000X1101X with 2 X's, we get 4 combinations:
-                //    000000000000000000000000000000(X)1101(X) becomes:
-                // 1. 000000000000000000000000000000(0)1101(0)
-                // 2. 000000000000000000000000000000(0)1101(1)
-                // 3. 000000000000000000000000000000(1)1101(0)
-                // 4. 000000000000000000000000000000(1)1101(1)
-
-                // with 3 it's 8 combinations.. and so on
-
                 // let's do this recursively
                 $posCombos = $this->maskTraverse($posMask);
                 foreach ($posCombos as $pos) {
@@ -94,6 +84,12 @@ public function solvePart2(): int|string|null
 
     /**
      * Recursively build up a list of all possible positions.
+     * Example: given a $posBin like 000000000000000000000000000000X1101X with 2 X's, we get 4 combinations:
+     *    000000000000000000000000000000(X)1101(X) becomes:
+     * 1. 000000000000000000000000000000(0)1101(0)
+     * 2. 000000000000000000000000000000(0)1101(1)
+     * 3. 000000000000000000000000000000(1)1101(0)
+     * 4. 000000000000000000000000000000(1)1101(1).
      *
      * @param string $posMask
      *
diff --git a/src/Day15.php b/src/Day15.php
@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App;
+
+use App\Interfaces\DayInterface;
+
+class Day15 extends DayBehaviour implements DayInterface
+{
+    public function solvePart1(): int|string|null
+    {
+        //$this->input[0] = '0,3,6';
+        //$this->input[0] = '3,1,2';
+        $turns = array_map('intval', str_getcsv(trim($this->input[0])));
+        $max   = 2020;
+        $i     = count($turns);
+        while ($i < $max) {
+            $last = $turns[count($turns) - 1];
+            $seen = array_slice(array_filter($turns, static fn (int $no) => $no === $last, ARRAY_FILTER_USE_BOTH), -2, 2, true);
+            if (1 === count($seen)) {
+                $next = 0;
+            } else {
+                $last2 = array_map(static fn (int $i) => $i + 1, array_keys($seen));
+                $next  = $last2[1] - $last2[0];
+            }
+            $turns[] = $next;
+            ++$i;
+        }
+
+        return $turns[count($turns) - 1];
+    }
+
+    public function solvePart2(): int|string|null
+    {
+        // TODO: Implement solvePart2() method.
+        return null;
+    }
+}
diff --git a/tests/Day14Test.php b/tests/Day14Test.php
@@ -17,5 +17,5 @@
 
 test('solves part2')
     ->expect(fn () => $this->day->solvePart2())
-    ->toBe(null)
+    ->toBe(2737766154126)
 ;
diff --git a/tests/Day15Test.php b/tests/Day15Test.php
@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+use App\DayFactory;
+use App\Interfaces\DayInterface;
+
+uses()->beforeEach(function (): void {
+    /* @var DayInterface day */
+    $this->day = DayFactory::create(getDayFromFile(__FILE__));
+});
+
+test('solves part1')
+    ->expect(fn () => $this->day->solvePart1())
+    ->toBe(614)
+;
+
+test('solves part2')
+    ->expect(fn () => $this->day->solvePart2())
+    ->toBe(null)
+;

Original file line number	Diff line number	Diff line change
`@@ -17,5 +17,5 @@`
`17`	`17`
`18`	`18`	`test('solves part2')`
`19`	`19`	`->expect(fn () => $this->day->solvePart2())`
`20`		`- ->toBe(null)`
	`20`	`+ ->toBe(2737766154126)`
`21`	`21`	`;`