Merge pull request #40 from hildjj/day20

Day 20

day20.peggy

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+lines = (@[#.SE]+ "\n")+
+

day20.ts

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+import { PointSet } from './lib/rect.ts';
+import { AllDirs, Point, PointMap, Rect } from './lib/rect.ts';
+import { type MainArgs, parseFile } from './lib/utils.ts';
+import { BinaryHeap } from '@std/data-structures';
+
+type Parsed = string[][];
+
+function astar(r: Rect, start: Point, end: Point): PointSet {
+  const gScore = new PointMap([[start, 0]]);
+  const fScore = new PointMap([[start, 0]]);
+  const prev = new PointMap<Point>();
+  const backlog = new BinaryHeap<Point>(
+    (a, b) => fScore.get(a)! - fScore.get(b)!,
+  );
+  backlog.push(start);
+
+  while (!backlog.isEmpty()) {
+    const p = backlog.pop()!;
+    const g = gScore.get(p)!;
+
+    if (p.equals(end)) {
+      const ps = new PointSet();
+      let n: Point | undefined = end;
+      while (n) {
+        ps.add(n);
+        n = prev.get(n);
+      }
+      return ps;
+    }
+
+    for (const d of AllDirs) {
+      const next = p.inDir(d);
+      if (r.check(next) && (r.get(next) !== '#')) {
+        const nextG = gScore.get(next) ?? Infinity;
+        if (g + 1 < nextG) {
+          gScore.set(next, g + 1);
+          fScore.set(next, g + next.manhattan(end));
+          backlog.push(next);
+          prev.set(next, p);
+        }
+      }
+    }
+  }
+
+  return new PointSet();
+}
+
+function part1(inp: Parsed): number {
+  const r = new Rect(inp);
+  const [start] = r.filter((v) => v === 'S');
+  const [end] = r.filter((v) => v === 'E');
+
+  const ps = astar(r, start, end);
+  const pss = ps.size;
+  const target = pss - 100;
+  let tot = 0;
+  let pcount = 0;
+  for (const p of ps) {
+    let qcount = 0;
+    for (const q of ps) {
+      if (p.equals(q)) {
+        continue;
+      }
+      const d = p.manhattan(q);
+      if (d === 2) {
+        if ((pcount + (pss - qcount) + 1) <= target) {
+          tot++;
+        }
+      }
+      qcount++;
+    }
+    pcount++;
+  }
+  return tot;
+}
+
+function part2(inp: Parsed): number {
+  const r = new Rect(inp);
+  const [start] = r.filter((v) => v === 'S');
+  const [end] = r.filter((v) => v === 'E');
+
+  const ps = astar(r, start, end);
+  const pss = ps.size;
+  const target = pss - 100;
+  let tot = 0;
+  let pcount = 0;
+  for (const p of ps) {
+    let qcount = 0;
+    for (const q of ps) {
+      if (p.equals(q)) {
+        continue;
+      }
+      const d = p.manhattan(q);
+      if (d <= 20) {
+        if ((pcount + (pss - qcount) + d - 1) <= target) {
+          tot++;
+        }
+      }
+      qcount++;
+    }
+    pcount++;
+  }
+  return tot;
+}
+
+export default async function main(args: MainArgs): Promise<[number, number]> {
+  const inp = await parseFile<Parsed>(args);
+  return [part1(inp), part2(inp)];
+}

test/day20.js

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+export default [1429, 988931];