2024 day 14

2024/day-14/day14.ts

@@ -0,0 +1,180 @@
+export function part1(input: string, width: number, height: number) {
+	const parsedInput = parseInput(input)
+	const positions = []
+	const quadrants = getQuadrants(width, height)
+	for (const robot of parsedInput) {
+		let pos = robot[0]
+		const velocity = robot[1]
+		for (let i = 0; i < 100; i++) {
+			pos = calculateNextPosition(pos, velocity, width, height)
+		}
+		positions.push(pos)
+	}
+	return getSafetyFactor(positions, quadrants)
+}
+
+function getSafetyFactor(
+	positions: [number, number][],
+	quadrants: ReturnType<typeof getQuadrants>,
+) {
+	let tr = 0
+	let tl = 0
+	let br = 0
+	let bl = 0
+
+	for (const position of positions) {
+		const res = determineQuadrant(position, quadrants)
+		switch (res) {
+			case "tr":
+				tr++
+				break
+			case "tl":
+				tl++
+				break
+			case "br":
+				br++
+				break
+			case "bl":
+				bl++
+				break
+			default:
+				break
+		}
+	}
+
+	return tr * tl * br * bl
+}
+
+export function part2(input: string, width: number, height: number) {
+	const parsedInput = parseInput(input)
+	const quadrants = getQuadrants(width, height)
+	let minsf = Number.POSITIVE_INFINITY
+	let best = 0
+	let bestPositions = []
+
+	let positions = parsedInput.map((x) => x[0])
+	for (let i = 0; i < width * height; i++) {
+		const currentPositions = []
+		for (let i1 = 0; i1 < parsedInput.length; i1++) {
+			const robot = parsedInput[i1]
+			const pos = positions[i1]
+			const velocity = robot[1]
+			const newPos = calculateNextPosition(pos, velocity, width, height)
+			currentPositions.push(newPos)
+		}
+		positions = currentPositions
+		const sf = getSafetyFactor(positions, quadrants)
+		if (sf < minsf) {
+			minsf = sf
+			best = i + 1
+			bestPositions = positions
+		}
+	}
+	display(bestPositions, width, height)
+	return best
+}
+
+function parseInput(input: string) {
+	const lines = input.split("\n")
+	return lines.map((line) => {
+		return line
+			.replaceAll("p=", "")
+			.replaceAll("v=", "")
+			.trim()
+			.split(" ")
+			.map((x) => x.split(",").map(Number))
+	}) as [number, number][][]
+}
+
+export function calculateNextPosition(
+	currentPosition: [number, number],
+	velocity: [number, number],
+	width: number,
+	height: number,
+) {
+	const [cx, cy] = currentPosition
+	const [vx, vy] = velocity
+
+	let nx = cx + vx
+	let ny = cy + vy
+	if (ny < 0) {
+		ny = height + ny
+	}
+	if (ny >= height) {
+		ny = ny - height
+	}
+	if (nx < 0) {
+		nx = width + nx
+	}
+	if (nx >= width) {
+		nx = nx - width
+	}
+	return [nx, ny] as [number, number]
+}
+
+function getQuadrants(width: number, height: number) {
+	const tl = {
+		fx: 0,
+		fy: 0,
+		tx: Math.floor(width / 2) - 1,
+		ty: Math.floor(height / 2) - 1,
+	}
+	const tr = {
+		fx: Math.ceil(width / 2),
+		fy: 0,
+		tx: width - 1,
+		ty: Math.floor(height / 2) - 1,
+	}
+	const bl = {
+		fx: 0,
+		fy: Math.ceil(height / 2),
+		tx: Math.floor(width / 2) - 1,
+		ty: height - 1,
+	}
+	const br = {
+		fx: Math.ceil(width / 2),
+		fy: Math.ceil(height / 2),
+		tx: width - 1,
+		ty: height - 1,
+	}
+	return { tl, tr, bl, br }
+}
+
+function determineQuadrant(
+	[x, y]: [number, number],
+	{ tr, tl, br, bl }: ReturnType<typeof getQuadrants>,
+) {
+	if (x >= tr.fx && x <= tr.tx) {
+		if (y >= tr.fy && y <= tr.ty) {
+			return "tr"
+		}
+		if (y >= br.fy && y <= br.ty) {
+			return "br"
+		}
+		return null
+	}
+	if (x >= tl.fx && x <= tl.tx) {
+		if (y >= tl.fy && y <= tl.ty) {
+			return "tl"
+		}
+		if (y >= bl.fy && y <= bl.ty) {
+			return "bl"
+		}
+		return null
+	}
+	return null
+}
+
+function display(positions: [number, number][], width: number, height: number) {
+	const grid = []
+	for (let i = 0; i < height; i++) {
+		const line = []
+		for (let j = 0; j < width; j++) {
+			if (positions.find(([x, y]) => x === j && y === i)) {
+				line.push("X")
+			} else line.push(".")
+		}
+		grid.push(line.join(""))
+	}
+	console.log(grid.join("\n"))
+}