solved day 20

Author: shahata

src/2024/day20.js

@@ -0,0 +1,45 @@
+function findPath(input) {
+  let map = input.split("\n").map(line => line.split(""));
+  let sy = map.findIndex(line => line.includes("S"));
+  let sx = map[sy].indexOf("S");
+  let ey = map.findIndex(line => line.includes("E"));
+  let ex = map[ey].indexOf("E");
+  let queue = [{ x: sx, y: sy }];
+  let visited = new Set([`${sx},${sy}`]);
+  let path = [];
+  map[ey][ex] = ".";
+  while (queue.length) {
+    let { x, y } = queue.shift();
+    path.push({ x, y });
+    if (x === ex && y === ey) break;
+    const neighbors = [
+      { x: x + 1, y },
+      { x: x - 1, y },
+      { x, y: y + 1 },
+      { x, y: y - 1 },
+    ].filter(({ x, y }) => map[y]?.[x] === "." && !visited.has(`${x},${y}`));
+    neighbors.forEach(({ x, y }) => {
+      visited.add(`${x},${y}`);
+      queue.push({ x, y });
+    });
+  }
+  return path;
+}
+
+export function part1(input, save = 100, cheat = 2) {
+  let path = findPath(input);
+  let count = 0;
+  for (let i = 0; i < path.length; i++) {
+    for (let j = i + save; j < path.length; j++) {
+      const distance =
+        Math.abs(path[j].x - path[i].x) + Math.abs(path[j].y - path[i].y);
+      const saved = j - i - distance;
+      if (saved >= save && distance <= cheat) count++;
+    }
+  }
+  return count;
+}
+
+export function part2(input, save = 100) {
+  return part1(input, save, 20);
+}

src/2024/day20.spec.js

@@ -0,0 +1,68 @@
+import { part1, part2 } from "./day20.js";
+import readInput from "../utils/read-input.js";
+
+const input = readInput(import.meta.url);
+
+describe("day20 2024", () => {
+  describe("part1", () => {
+    test("it should work for part 1 examples", () => {
+      expect(
+        part1(
+          [
+            "###############",
+            "#...#...#.....#",
+            "#.#.#.#.#.###.#",
+            "#S#...#.#.#...#",
+            "#######.#.#.###",
+            "#######.#.#...#",
+            "#######.#.###.#",
+            "###..E#...#...#",
+            "###.#######.###",
+            "#...###...#...#",
+            "#.#####.#.###.#",
+            "#.#...#.#.#...#",
+            "#.#.#.#.#.#.###",
+            "#...#...#...###",
+            "###############",
+          ].join("\n"),
+          2,
+        ),
+      ).toEqual(44);
+    });
+
+    test("it should work for part 1 input", () => {
+      expect(part1(input)).toEqual(1459);
+    });
+  });
+
+  describe("part2", () => {
+    test("it should work for part 2 examples", () => {
+      expect(
+        part2(
+          [
+            "###############",
+            "#...#...#.....#",
+            "#.#.#.#.#.###.#",
+            "#S#...#.#.#...#",
+            "#######.#.#.###",
+            "#######.#.#...#",
+            "#######.#.###.#",
+            "###..E#...#...#",
+            "###.#######.###",
+            "#...###...#...#",
+            "#.#####.#.###.#",
+            "#.#...#.#.#...#",
+            "#.#.#.#.#.#.###",
+            "#...#...#...###",
+            "###############",
+          ].join("\n"),
+          50,
+        ),
+      ).toEqual(285);
+    });
+
+    test("it should work for part 2 input", () => {
+      expect(part2(input)).toEqual(1016066);
+    });
+  });
+});

src/2024/day20.txt

@@ -22,7 +22,7 @@ <h1 class="title-global"><a href="index.html">Advent of Code</a></h1>
         </nav>
         <div class="user">Shahar Talmi <a class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a> <a
             href="https://www.wix.engineering/" target="_blank" class="sponsor-badge"
-            title="Member of sponsor: Wix Engineering">(Sponsor)</a> <span class="star-count">38*</span></div>
+            title="Member of sponsor: Wix Engineering">(Sponsor)</a> <span class="star-count">40*</span></div>
       </div>
       <div>
         <h1 class="title-event">&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">$year=</span><a
@@ -32,7 +32,7 @@ <h1 class="title-event">&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">$year=<
     <main>
       <article>
 <p>From here, you can access all of the events (and the corresponding puzzles, leaderboards, stats, etc) ever run on Advent of Code:</p>
-<div class="eventlist-event"><a href="../2024/solver.html">[2024]</a> <span class="star-count">38*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
+<div class="eventlist-event"><a href="../2024/solver.html">[2024]</a> <span class="star-count">40*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
 <div class="eventlist-event"><a href="../2023/solver.html">[2023]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
 <div class="eventlist-event"><a href="../2022/solver.html">[2022]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
 <div class="eventlist-event"><a href="../2021/solver.html">[2021]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
@@ -42,7 +42,7 @@ <h1 class="title-event">&nbsp;&nbsp;&nbsp;<span class="title-event-wrap">$year=<
 <div class="eventlist-event"><a href="../2017/solver.html">[2017]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
 <div class="eventlist-event"><a href="../2016/solver.html">[2016]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
 <div class="eventlist-event"><a href="../2015/solver.html">[2015]</a> <span class="star-count">50*</span> <a  class="supporter-badge" title="Advent of Code Supporter">(AoC++)</a></div>
-<p>Total stars: <span class="star-count">488*</span></article>
+<p>Total stars: <span class="star-count">490*</span></article>
     </main>
   </body>
 </html>