Day 16

2024/16/index.ts

@@ -91,7 +91,6 @@ function fillDeadEnd(pos: Coord): void {
     };
 }
 
-printMap();
 for (let y = 1; y < height - 1; y++) {
     for (let x = 1; x < width - 1; x++) {
         const pos = { x, y };
@@ -104,29 +103,30 @@ for (let y = 1; y < height - 1; y++) {
         }
     }
 }
-printMap();
 
 let fastest: number|null = null;
 
 const scoreCache: { [key: string]: [number, Coord, Dir] } = {};
 
-const scores: Array<number> = [];
+const branchCache: { [key: string]: number } = {};
+
+const scores: Array<[number, Array<string>]> = [];
 
 function getScoresAfterPosition(pos: Coord, dir: Dir, currentScore = 0, path: Array<string> = [], lastBranch: [number, Coord]|null = null): void {
     if (fastest !== null && currentScore >= fastest) {
         return;
     }
-    const cache = scoreCache[`${pos.x},${pos.y}`];
-    if (cache) {
-        currentScore += cache[0];
-        pos = cache[1];
-        dir = cache[2];
-    }
     const branch = isBranch(pos, dir);
     if (branch) {
+        const cacheKey = `${pos.x},${pos.y},${dir}`;
+        const cache = branchCache[cacheKey];
+        if (cache && cache < currentScore) {
+            return;
+        } else {
+            branchCache[cacheKey] = currentScore;
+        }
         if (lastBranch) {
             scoreCache[`${lastBranch[1].x},${lastBranch[1].y}`] = [currentScore - lastBranch[0], pos, dir];
-            console.log(scoreCache);
         }
         lastBranch = [currentScore, pos];
     }
@@ -142,7 +142,7 @@ function getScoresAfterPosition(pos: Coord, dir: Dir, currentScore = 0, path: Ar
                     fastest = score;
                 }
                 lastBranch = null;
-                scores.push(score);
+                scores.push([score, [...path, nextStr]]);
                 return;
             } else if (nextChar === '.') {
                 getScoresAfterPosition(next, newDir, score, [...path, nextStr], branch ? [score, next] : lastBranch);
@@ -155,4 +155,13 @@ function getScoresAfterPosition(pos: Coord, dir: Dir, currentScore = 0, path: Ar
 
 getScoresAfterPosition(snakePos, snakeDir);
 
-console.log(Math.min(...scores));
+const fastestScore = Math.min(...scores.map(([score]) => score));
+
+let coordsOnPaths: Set<string> = new Set();
+scores.forEach(([score, path]) => {
+    if (score === fastestScore) {
+        path.forEach((coord) => coordsOnPaths.add(coord));
+    }
+});
+
+console.log(coordsOnPaths.size + 1);