[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) }),
 
 }
 

input/day/12-example.http

@@ -0,0 +1,52 @@
+POST http://localhost:5001/advent-of-code-2021-911a8/europe-west1/day-12
+Content-Type: text/plain
+
+start-A
+start-b
+A-c
+A-b
+b-d
+A-end
+b-end
+
+###
+
+POST http://localhost:5001/advent-of-code-2021-911a8/europe-west1/day-12
+Content-Type: text/plain
+
+dc-end
+HN-start
+start-kj
+dc-start
+dc-HN
+LN-dc
+HN-end
+kj-sa
+kj-HN
+kj-dc
+
+###
+
+POST http://localhost:5001/advent-of-code-2021-911a8/europe-west1/day-12
+Content-Type: text/plain
+
+fs-end
+he-DX
+fs-he
+start-DX
+pj-DX
+end-zg
+zg-sl
+zg-pj
+pj-he
+RW-he
+fs-DX
+pj-RW
+zg-RW
+start-pj
+he-WI
+zg-he
+pj-fs
+start-RW
+
+###

input/day/12.http

@@ -0,0 +1,30 @@
+POST http://localhost:5001/advent-of-code-2021-911a8/europe-west1/day-12
+Content-Type: text/plain
+
+start-kc
+pd-NV
+start-zw
+UI-pd
+HK-end
+UI-kc
+pd-ih
+ih-end
+start-UI
+kc-zw
+end-ks
+MF-mq
+HK-zw
+LF-ks
+HK-kc
+ih-HK
+kc-pd
+ks-pd
+MF-pd
+UI-zw
+ih-NV
+ks-HK
+MF-kc
+zw-NV
+NV-ks
+
+###