hsegnitz
diff --git a/‎php/2023/17/01.php
Lines changed: 113 additions & 0 deletions b/‎php/2023/17/01.php
Lines changed: 113 additions & 0 deletions
diff --git a/‎php/2023/17/example.txt
203 Bytes b/‎php/2023/17/example.txt
203 Bytes
diff --git a/‎php/2023/17/input.txt
19.6 KB b/‎php/2023/17/input.txt
19.6 KB
@@ -0,0 +1,113 @@
+<?php
+
+namespace Year2023\Day17;
+
+$start = microtime(true);
+
+$in = file_get_contents('example.txt', FILE_IGNORE_NEW_LINES);
+#$in = file_get_contents('input.txt', FILE_IGNORE_NEW_LINES);
+
+class AdventOfHeap extends \SplMinHeap
+{
+    protected function compare(mixed $value1, mixed $value2): int
+    {
+        return $value2['distance'] - $value1['distance'];
+    }
+}
+
+
+class Solver {
+
+    private array $map = [];
+    private array $visited = [];
+    private AdventOfHeap $heap;
+    private string $finalCoord;
+
+    private const DELTAS = [
+        'N' => ['x' =>  0, 'y' => -1],
+        'E' => ['x' =>  1, 'y' =>  0],
+        'S' => ['x' =>  0, 'y' =>  1],
+        'W' => ['x' => -1, 'y' =>  0],
+    ];
+
+    public function __construct(string $input)
+    {
+        $rows = explode("\n", $input);
+        foreach ($rows as $row) {
+            $this->map[] = str_split(trim($row));
+        }
+
+        $this->finalCoord = count($this->map[0])-1 . "," . count($this->map)-1;
+
+        $this->heap = new AdventOfHeap();
+        $this->heap->insert(['x' => 0, 'y' => 0, 'distance' => 0, 'direction' => 'E']);
+        $this->heap->insert(['x' => 0, 'y' => 0, 'distance' => 0, 'direction' => 'S']);
+    }
+
+    private function getNeighbours(int $x, int $y, string $originalDirection): \Generator
+    {
+        switch ($originalDirection) {
+            case "N":
+            case "S":
+                yield from $this->getNeighboursInDirection($x, $y, 'E');
+                yield from $this->getNeighboursInDirection($x, $y, 'W');
+                break;
+            case "E":
+            case "W":
+                yield from $this->getNeighboursInDirection($x, $y, 'N');
+                yield from $this->getNeighboursInDirection($x, $y, 'S');
+                break;
+            default:
+                throw new \RuntimeException('invalid direction');
+        }
+    }
+
+    private function getNeighboursInDirection(int $x, int $y, string $direction): \Generator
+    {
+        $distance = 0;
+        for ($i = 1; $i <= 3; $i++) {
+            $x += self::DELTAS[$direction]['x'];
+            $y += self::DELTAS[$direction]['y'];
+            if (isset($this->map[$y][$x])) {
+                $distance += $this->map[$y][$x];
+                yield ['x' => $x, 'y' => $y, 'distance' => $distance, 'direction' => $direction];
+            }
+        }
+    }
+
+    public function walk(): void
+    {
+        while (true) {
+            $current = $this->heap->extract();
+
+            foreach ($this->getNeighbours($current['x'], $current['y'], $current['direction']) as $next) {
+                $coord = $next['x'] . "," .  $next['y'];
+#                $coordDir = $next['x'] . "," .  $next['y'] . "," . $next['direction'];
+                if (isset($this->visited[$coord])) {  // && $this->visited[$coord]['direction'] === $next['direction']
+                    continue;
+                }
+                $next['distance'] += $current['distance'];
+                $this->heap->insert($next);
+                $this->visited[$coord] = ['distance' => $next['distance'], 'direction' => $next['direction']];
+
+                if ($coord === $this->finalCoord) {
+                    return;
+                }
+            }
+        }
+    }
+
+    public function getDistanceOfFinalTile(): int
+    {
+        return $this->visited[$this->finalCoord]['distance'];
+    }
+}
+
+$solver = new Solver($in);
+
+$solver->walk();
+
+echo $solver->getDistanceOfFinalTile();
+
+
+echo "\n", (microtime(true) - $start), "\n";