day11 part1 solved

jthatch · jthatch · commit aff1e76a0422 · 2021-10-02T17:51:53.000+01:00
diff --git a/Makefile b/Makefile
@@ -90,7 +90,7 @@ shell: ## Launch a shell into the docker container
 	$(DOCKER_RUN_PHP) /bin/bash
 
 xdebug: ## Launch a php container with xdebug (port 10000)
-	@$(DOCKER_RUN_PHP_XDEBUG) php run.php
+	@$(DOCKER_RUN_PHP_XDEBUG) php run.php $(onlyThisDay)
 
 xdebug-shell: ## Launch a php container with xdebug in a shell (port 10000)
 	@echo -e "=== Xdebug Launch Instructions ===\nAt the prompt type:\nphp run.php [day]\n\n"
diff --git a/README.md b/README.md
@@ -36,7 +36,7 @@ If you fancy having a go at the challenges yourself feel free to use this repo a
 `make run day={N}` e.g. `make run day=1`
 
 **Use XDebug**  
-`make xdebug` at the shell type: `vendor/bin/pest`  
+`make xdebug`  
 
 IDE settings:
 - `10000` - xdebug port 
diff --git a/src/Day11.php b/src/Day11.php
@@ -8,21 +8,23 @@
 
 class Day11 extends DayBehaviour implements DayInterface
 {
-    protected function applyRulesToSeats(array $seats): array
-    {
-        return [];
-    }
+    protected int $i = 0;
 
     /**
      * All decisions are based on the number of occupied seats adjacent to a given seat
      * (one of the eight positions immediately up, down, left, right, or diagonal from the seat).
      * The following rules are applied to every seat simultaneously:.
+     * Rules:
+     * If a seat is empty (L) and there are no occupied seats adjacent to it, the seat becomes occupied.
+     * If a seat is occupied (#) and four or more seats adjacent to it are also occupied, the seat becomes empty.
+     *
+     * Simulate your seating area by applying the seating rules repeatedly until no seats change state. How many seats end up occupied?
      *
      * @return int|null
      */
     public function solvePart1(): ?int
     {
-        $this->input = [
+        /*$this->input = [
             'L.LL.LL.LL',
             'LLLLLLL.LL',
             'L.L.L..L..',
@@ -33,21 +35,73 @@ public function solvePart1(): ?int
             'LLLLLLLLLL',
             'L.LLLLLL.L',
             'L.LLLLL.LL',
-        ];
-        $this->input = array_map(static fn (string $s): string => trim($s), $this->input);
-        $i           = 0;
-        /*while(true) {
-            $seatsChanged = 0;
+        ];*/
+        // convert into [y][x] array
+        $this->input      = array_map(static fn (string $s): array => str_split(trim($s)), $this->input);
+        $finalSeatingPlan = $this->seatTraverse();
+        $occupied         = array_filter(array_merge(...$finalSeatingPlan), static fn (string $s) => '#' === $s);
+
+        return count($occupied);
+    }
 
-            foreach($this->input as &$row) {
-                $adjacent = '';
-                array_walk($row, static function(string $s) use (&$seatsChanged) {
+    protected function seatTraverse(?array $seatLayout = null): array
+    {
+        ++$this->i;
+        // final recursive check
+        if ($seatLayout === $this->input) {
+            return $this->input;
+        }
+
+        // if we haven't been seeded then start with input
+        $this->input = $seatLayout ?? $this->input;
 
-                });
+        $newInput = $this->input; // clone it, we'll make all changes to the new input
+        for ($y = 0, $yMax = count($this->input); $y < $yMax; ++$y) {
+            for ($x = 0, $xMax = count($this->input[$y]); $x < $xMax; ++$x) {
+                $adjacentSeats = [
+                    // above
+                    $this->input[$y - 1][$x - 1] ?? '',
+                    $this->input[$y - 1][$x] ?? '',
+                    $this->input[$y - 1][$x + 1] ?? '',
+                    // below
+                    $this->input[$y + 1][$x - 1] ?? '',
+                    $this->input[$y + 1][$x] ?? '',
+                    $this->input[$y + 1][$x + 1] ?? '',
+                    // left
+                    $this->input[$y][$x - 1] ?? '',
+                    // right
+                    $this->input[$y][$x + 1] ?? '',
+                ];
+                $occupiedAdjacent = array_filter($adjacentSeats, static fn (string $v) => '#' === $v);
+                $seat             = $this->input[$y][$x];
+                switch ($seat) { // faster than using match
+                    case '.':
+                        continue 2;
+                    case 'L':
+                        if (empty($occupiedAdjacent)) {
+                            $newInput[$y][$x] = '#';
+                        }
+                        break;
+                    case '#':
+                        if (4 <= count($occupiedAdjacent)) {
+                            $newInput[$y][$x] = 'L';
+                        }
+                        break;
+                }
             }
+            /*printf("y: %d\n%s\n%s\n",
+                $y,
+                implode('', $this->input[$y]),
+                implode('', $newInput[$y]),
+            );*/
         }
-        print_r($this->input);*/
-        return null;
+        /*printf("%d: new: %d old: %d\n",
+            $this->i,
+            count(array_filter(array_merge(...$newInput), static fn (string $s) => '#' === $s)),
+            count(array_filter(array_merge(...$this->input), static fn (string $s) => '#' === $s)),
+        );*/
+
+        return $this->seatTraverse($newInput);
     }
 
     public function solvePart2(): ?int
