[TASK] Solved Day 12

functions/src/day12.ts

@@ -0,0 +1,72 @@
+import Day from "./day";
+
+class Day12 implements Day {
+
+  part1(input: string[]): number | string {
+
+    const caves = this.parseInput(input);
+    return this.countPaths("start", caves, []);
+  }
+
+
+  part2(input: string[]): number | string {
+
+    const caves = this.parseInput(input);
+    return this.countPaths("start", caves, [], true);
+  }
+
+  private parseInput(input: string[]) {
+    const caves = new Map<string, string[]>();
+    for (const line of input) {
+      const splitIndex = line.indexOf("-");
+      const from = line.substr(0, splitIndex);
+      const to = line.substr(splitIndex + 1);
+
+      this.addPath(from, to, caves);
+      this.addPath(to, from, caves);
+    }
+    return caves;
+  }
+
+  addPath(from: string, to: string, caves: Map<string, string[]>) {
+    const existing = caves.get(from);
+    if (existing) {
+      existing.push(to);
+    } else {
+      caves.set(from, [to]);
+    }
+  }
+
+  countPaths(pos: string, caves: Map<string, string[]>, visited: string[], secondSmallVisitAllowed: boolean = false): number {
+
+    // If we reached the end, there is exactly one path
+    if (pos === "end") return 1;
+
+    const destinations = caves.get(pos);
+    if (!destinations) {
+      throw Error(`No paths from ${pos}`);
+    }
+
+    const newVisited = [...visited];
+    if (this.isSmall(pos)) {
+      newVisited.push(pos);
+    }
+
+    let sum = 0;
+    for (const destination of destinations) {
+      if (!this.isSmall(destination) || !visited.includes(destination)) {
+        sum += this.countPaths(destination, caves, newVisited, secondSmallVisitAllowed)
+      } else if (secondSmallVisitAllowed && destination !== "start") {
+        sum += this.countPaths(destination, caves, newVisited, false)
+      }
+    }
+
+    return sum;
+  }
+
+  isSmall(cave: string) {
+    return cave.toLowerCase() === cave;
+  }
+}
+
+export default Day12;

functions/src/index.ts

@@ -13,6 +13,7 @@ import Day8 from "./day8";
 import Day9 from "./day9";
 import Day10 from "./day10";
 import Day11 from "./day11";
+import Day12 from "./day12";
 
 
 // // Start writing Firebase Functions
@@ -40,6 +41,7 @@ export const day = {
   9: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day9(), request, response) }),
   10: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day10(), request, response) }),
   11: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day11(), request, response) }),
+  12: functions.region("europe-west1").https.onRequest((request, response) => { processDay(new Day12(), request, response) }),
 
 }
 
@@ -56,4 +58,4 @@ function sendResponse(response: Response, part1: string | number, part2: string
 
   const res: DayResult = { part1, part2 };
   response.send(res);
-}
+}