Day Six complete

src/day_six.test.ts

@@ -0,0 +1,21 @@
+import {BoatRace, Race} from "./day_six";
+
+describe('Day Six', () => {
+	const input = `Time:      7  15   30
+Distance:  9  40  200`;
+
+	it.each([
+		[[7, 9], 4],
+		[[15, 40], 8],
+		[[30, 200], 9],
+		[[71530, 940200], 71503]
+	])('should calculate that race %s could be won %s different ways', (race, expected) => {
+		const boatRace = new BoatRace(input);
+		expect(boatRace.numberOfWinningMethods(race as Race)).toEqual(expected);
+	});
+
+	it('should calculate the total number of winning methods', () => {
+		const boatRace = new BoatRace(input);
+		expect(boatRace.totalNumberOfWaysToBeatRace()).toEqual(71503);
+	})
+});

src/day_six.ts

@@ -0,0 +1,43 @@
+import {anyCharOf, spaces1, string, whitespace} from "parjs";
+import {between, exactly, manySepBy, stringify, then} from "parjs/combinators";
+import {Range} from "immutable";
+import fs from "fs";
+
+export type Race = [number, number];
+
+const timeName = string('Time:').pipe(then(spaces1()));
+const distanceName = string('Distance:').pipe(then(spaces1()));
+
+const timeParser = anyCharOf("0123456789").pipe(manySepBy(whitespace().pipe(exactly(2))), stringify(), between(timeName, whitespace()));
+const distanceParser = anyCharOf("0123456789").pipe(manySepBy(whitespace().pipe(exactly(2))), stringify(), between(distanceName, whitespace()));
+
+const parser = timeParser.pipe(then(distanceParser));
+
+
+export class BoatRace {
+	private readonly race: Race;
+
+	constructor(input: string) {
+		const [times, distances] = parser.parse(input).value;
+		this.race = [parseInt(times), parseInt(distances)];
+	}
+
+	numberOfWinningMethods = (race: Race): number => {
+		const [time, distance] = race;
+
+		const canWin = (holdingTime: number) => ((time - holdingTime) * holdingTime) > distance;
+
+		const range = Range(0, time).filter(canWin).cacheResult();
+		return range.size || 0;
+	}
+
+	public totalNumberOfWaysToBeatRace(): number {
+		return this.numberOfWinningMethods(this.race);
+	}
+}
+
+export const runDaySix = () => {
+	const input = fs.readFileSync('./inputs/day_six_input.txt', 'utf-8').trimEnd();
+	const races = new BoatRace(input);
+	console.log(races.totalNumberOfWaysToBeatRace());
+}