saving original implementation for the history books :)

src/2024/day20.js

@@ -26,7 +26,7 @@ function findPath(input) {
   return path;
 }
 
-export function part1(input, save = 100, cheat = 2) {
+function countCheats(input, save, cheat) {
   const distance = (a, b) => Math.abs(a.x - b.x) + Math.abs(a.y - b.y);
   let path = findPath(input);
   let count = 0;
@@ -39,6 +39,66 @@ export function part1(input, save = 100, cheat = 2) {
   return count;
 }
 
+function countCheatsOriginal(input, save, cheat) {
+  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, steps: 0 }];
+  let visited = new Set([`${sx},${sy}`]);
+  let distance = new Map();
+  map[ey][ex] = ".";
+  while (queue.length) {
+    let { x, y, steps } = queue.shift();
+    distance.set(`${x},${y}`, steps);
+    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, steps: steps + 1 });
+    });
+  }
+  let count = 0;
+  queue = [{ x: sx, y: sy, steps: 0, jumped: 0, v: null }];
+  while (queue.length) {
+    let { x, y, steps, jumped, v } = queue.shift();
+    if (distance.get(`${x},${y}`) !== null) {
+      if (jumped === 0 && distance.get(`${x},${y}`) - steps < 0) continue;
+      if (distance.get(`${x},${y}`) - steps >= save) count++;
+    }
+    if (jumped === cheat) continue;
+    v = v || new Set([`${x},${y}`]);
+    const neighbors = [
+      { x: x + 1, y },
+      { x: x - 1, y },
+      { x, y: y + 1 },
+      { x, y: y - 1 },
+    ].filter(({ x, y }) => map[y]?.[x] !== undefined);
+    neighbors.forEach(({ x, y }) => {
+      if (jumped === 0 && map[y][x] !== "#") {
+        queue.push({ x, y, steps: steps + 1, jumped: 0, v: null });
+      }
+      if (!v.has(`${x},${y}`)) {
+        v.add(`${x},${y}`);
+        queue.push({ x, y, steps: steps + 1, jumped: jumped + 1, v });
+      }
+    });
+  }
+  return count;
+}
+
+export function part1(input, save = 100) {
+  countCheats(input, save, 2);
+  return countCheatsOriginal(input, save, 2);
+}
+
 export function part2(input, save = 100) {
-  return part1(input, save, 20);
+  countCheats(input, save, 20);
+  return countCheatsOriginal(input, save, 20);
 }