part 2

2022/09/bigSample

@@ -0,0 +1,8 @@
+R 5
+U 8
+L 8
+D 3
+R 17
+D 10
+L 25
+U 20

2022/09/part1.js

@@ -2,37 +2,36 @@ import * as R from "remeda";
 import Victor from "@a-robu/victor";
 
 import { readFile } from "../05/part1.js";
-import { passthru } from '../08/part1.js'
+import { passthru } from "../08/part1.js";
 
 const directions = {
   R: new Victor(1, 0),
   L: new Victor(-1, 0),
   U: new Victor(0, 1),
   D: new Victor(0, -1),
-}
+};
 
 const parseLine = R.createPipe(
-    line => line.split(" "),
+  (line) => line.split(" "),
   ([direction, times]) => Array(parseInt(times)).fill(directions[direction])
 );
 
-
-const readInput = (...args) => R.pipe(
+export const readInput = (...args) =>
+  R.pipe(
     readFile(...args),
-  text => text.split("\n"),
+    (text) => text.split("\n"),
     R.compact,
     R.map(parseLine),
-  R.flatten,
-)
+    R.flatten
+  );
 
 export const puzzleInput = readInput(import.meta.url, "input");
 export const sample = readInput(import.meta.url, "sample");
 
-const touching = (v1,v2) => [v1.distanceX(v2), v1.distanceY(v2)].every(
-    x => x*x <= 1
-);
+export const touching = (v1, v2) =>
+  [v1.distanceX(v2), v1.distanceY(v2)].every((x) => x * x <= 1);
 
-export function moveOnce( head, tail, d ) {
+export const moveOnce = (head, tail) => (d) => {
   head.add(d);
 
   if (touching(head, tail)) return tail.toString();
@@ -47,21 +46,14 @@ export function moveOnce( head, tail, d ) {
   tail.add(delta);
 
   return tail.toString();
-}
+};
 
 const moveAround = (directives) => {
   const head = new Victor(0, 0);
   const tail = new Victor(0, 0);
 
-    const move = d => moveOnce(head,tail,d);
-    return [
-        tail.toString(),
-        ...directives.map( move )
-    ]
+  const move = moveOnce(head, tail);
+  return directives.map(move);
 };
 
-export default R.createPipe(
-    moveAround,
-    R.uniq,
-    moves => moves.length
-);
+export default R.createPipe(moveAround, R.uniq, (moves) => moves.length);

2022/09/part2.js

@@ -1,4 +1,36 @@
 import * as R from "remeda";
+import Victor from "@a-robu/victor";
 
+import { touching, readInput } from "./part1.js";
 
-export default () => {};
+export const bigSample = readInput(import.meta.url, "bigSample");
+
+export const moveOnce = (knots) => (d) => {
+  R.first(knots).add(d);
+
+  for (const i of R.range(1, knots.length)) {
+    if (touching(knots[i - 1], knots[i])) break;
+
+    const delta = knots[i - 1].clone().subtract(knots[i]).normalize();
+
+    if (delta.x * delta.y) {
+      delta.x = delta.x > 0 ? 1 : -1;
+      delta.y = delta.y > 0 ? 1 : -1;
+    }
+
+    knots[i].add(delta);
+  }
+
+  return R.last(knots).toString();
+};
+
+const moveAround = (directives) => {
+  const knots = Array(10)
+    .fill(null)
+    .map(() => new Victor(0, 0));
+
+  const move = moveOnce(knots);
+  return directives.map(move);
+};
+
+export default R.createPipe(moveAround, R.uniq, (moves) => moves.length);

2022/09/test.js

@@ -5,36 +5,40 @@ const V = (...args) => new Victor(...args);
 
 import { expectSolution } from "../01/main.js";
 import part1, { moveOnce, sample, puzzleInput } from "./part1.js";
-import part2 from "./part2.js";
+import part2, { bigSample } from "./part2.js";
 
 describe("part 1", () => {
   test("moveOnce", () => {
     let head = V(1, 0);
     let tail = V(0, 0);
-        moveOnce(head,tail,V(1,0));
+    moveOnce(head, tail)(V(1, 0));
 
     expect(tail).toMatchObject({ x: 1, y: 0 });
 
-        moveOnce(head,tail,V(0,1));
+    moveOnce(head, tail)(V(0, 1));
 
     expect(tail).toMatchObject({ x: 1, y: 0 });
 
-        moveOnce(head,tail,V(0,1));
+    moveOnce(head, tail)(V(0, 1));
 
     expect(tail).toMatchObject({ x: 2, y: 1 });
-
   });
 
   test("sample", () => {
     expect(part1(sample)).toEqual(13);
-    } )
+  });
   test("solution", () => {
     expectSolution(part1(puzzleInput)).toEqual(6030);
   });
 });
 
 describe("part 2", () => {
-  test.todo("solution", () => {
-    expectSolution(part2(puzzleInput)).toEqual("TODO");
+  test("sample", () => {
+    expect(part2(sample)).toEqual(1);
+    expect(part2(bigSample)).toEqual(36);
+  });
+
+  test("solution", () => {
+    expectSolution(part2(puzzleInput)).toEqual(2545);
   });
 });