Day 21 Part 1

Typescript/2023/src/days/__test__/day21.test.ts

@@ -0,0 +1,8 @@
+import { SolvePartOne } from "../day21/day21";
+import { describe, expect, test } from "vitest";
+
+describe("Day 21 Part 01", () => {
+  test("Expected result", () => {
+    expect(SolvePartOne()).toBe(16);
+  });
+});

Typescript/2023/src/days/day21/day21.ts

@@ -0,0 +1,92 @@
+import * as fs from "fs";
+import { GetPointKey, Point } from "../../util/coords";
+
+import { Queue } from "data-structure-typed";
+
+const isSample = true;
+
+interface GardenPosition extends Point {
+  symbol: string;
+}
+
+function parseMap(input: string[][]): [Map<string, GardenPosition>, Point] {
+  const gardenMap = new Map<string, GardenPosition>();
+  const startPos: Point = { X: 0, Y: 0 };
+  for (let y = 0; y < input.length; y++) {
+    for (let x = 0; x < input[0].length; x++) {
+      const symbol = input[y][x];
+      gardenMap.set(GetPointKey({ X: x, Y: y }), { symbol: symbol, X: x, Y: y });
+      if (symbol === "S") {
+        startPos.X = x;
+        startPos.Y = y;
+      }
+    }
+  }
+  return [gardenMap, startPos];
+}
+
+export function SolvePartOne(): number {
+  const fileName = isSample ? "/src/days/day21/sample.txt" : "/src/days/day21/full.txt";
+  const lines = fs
+    .readFileSync(process.cwd() + fileName, "utf8")
+    .split("\n")
+    .map((l) => l.split(""));
+
+  const [map, start] = parseMap(lines);
+  const result = getPossibleEndpoints(map, start, lines[0].length, lines.length);
+  return result;
+}
+
+function getPossibleEndpoints(map: Map<string, GardenPosition>, start: Point, xBound: number, yBound: number): number {
+  const deltas: Point[] = [
+    { X: 1, Y: 0 },
+    { X: -1, Y: 0 },
+    { X: 0, Y: 1 },
+    { X: 0, Y: -1 }
+  ];
+  const maxSteps = isSample ? 6 : 64;
+  const reachedPositions = new Set<string>();
+  const Q = new Queue<string>();
+  const visited = new Set<string>();
+  Q.enqueue(makePointWithStepKey(start, 0));
+  visited.add(makePointWithStepKey(start, 0));
+  while (Q.size > 0) {
+    const v: string = Q.dequeue()!;
+    const [vPoint, stepsAtPoint] = getPointWithStepFromKey(v);
+    if (stepsAtPoint === maxSteps) {
+      reachedPositions.add(makePointWithStepKey(vPoint, stepsAtPoint));
+    }
+    if (stepsAtPoint === maxSteps + 1) {
+      return reachedPositions.size;
+    }
+    deltas.forEach((delta) => {
+      const nextPoint: Point = { X: vPoint.X + delta.X, Y: vPoint.Y + delta.Y };
+
+      //Is Next Point in Map && not Wall
+      if (0 <= nextPoint.X && nextPoint.X < xBound && 0 <= nextPoint.Y && nextPoint.Y < yBound) {
+        if (map.get(GetPointKey(nextPoint))!.symbol !== "#") {
+          const key = makePointWithStepKey(nextPoint, stepsAtPoint + 1);
+          if (!visited.has(key)) {
+            Q.enqueue(key);
+            visited.add(key);
+          }
+        }
+      }
+    });
+  }
+  return -1;
+}
+
+export function SolvePartTwo(): number {
+  console.log("TBD");
+  return 0;
+}
+
+function getPointWithStepFromKey(key: string): [Point, number] {
+  const split = key.split(":");
+  return [{ X: Number(split[0]), Y: Number(split[1]) }, Number(split[2])];
+}
+
+function makePointWithStepKey(p: Point, step: number): string {
+  return `${p.X}:${p.Y}:${step}`;
+}

Typescript/2023/src/days/day21/sample.txt

@@ -0,0 +1,11 @@
+...........
+.....###.#.
+.###.##..#.
+..#.#...#..
+....#.#....
+.##..S####.
+.##..#...#.
+.......##..
+.##.#.####.
+.##..##.##.
+...........

Typescript/2023/src/main.ts

@@ -18,9 +18,9 @@ import { SolvePartOne as SolvePartOneD17, SolvePartTwo as SolvePartTwoD17 } from
 import { SolvePartOne as SolvePartOneD18, SolvePartTwo as SolvePartTwoD18 } from "./days/day18/day18";
 import { SolvePartOne as SolvePartOneD19, SolvePartTwo as SolvePartTwoD19 } from "./days/day19/day19";
 import { SolvePartOne as SolvePartOneD20, SolvePartTwo as SolvePartTwoD20 } from "./days/day20/day20";
-
+import { SolvePartOne as SolvePartOneD21, SolvePartTwo as SolvePartTwoD21 } from "./days/day21/day21";
 //Please don't look at this file I dont care its ugly
-const day: number = 20;
+const day: number = 21;
 
 if (day === 1) {
   console.log("Day 01 Part 01: " + SolvePartOne());
@@ -82,4 +82,7 @@ if (day === 1) {
 } else if (day === 20) {
   console.log("Day 20 Part 01: " + SolvePartOneD20());
   console.log("Day 20 Part 02: " + SolvePartTwoD20());
+} else if (day === 21) {
+  console.log("Day 21 Part 01: " + SolvePartOneD21());
+  console.log("Day 21 Part 02: " + SolvePartTwoD21());
 }