Day 10

Author: ansf

Makefile

@@ -42,3 +42,8 @@ day9:
 	npx ts-node day9.ts
 day9-2:
 	npx ts-node day9-2.ts
+
+day10:
+	npx ts-node day10.ts
+day10-2:
+	npx ts-node day10-2.ts

day10-2.ts

@@ -0,0 +1,107 @@
+import * as fs from "fs"
+import { fileURLToPath } from "url"
+
+const abs = Math.abs
+
+function flip<T>(a: T[][]) {
+	const flipped = Array.from(Array(a[0].length)).map(() => Array.from(Array(a.length)))
+	for (let x = 0; x < flipped.length; x++) {
+		for (let y = 0; y < flipped[0].length; y++) {
+			flipped[x][y] = a[y][x]
+		}
+	}
+	return flipped
+}
+
+function print<T>(a: T[][]) {
+	for (let y = 0; y < a[0].length; y++) {
+		console.log(Array(a.length).fill(0).map((_, x) => a[x][y]).join(""))
+	}
+}
+
+function gcd(a: number, b: number) {
+	if (a == 0) return abs(b)
+	if (b == 0) return abs(a)
+
+	let h: number
+	do {
+		h = a % b
+		a = b
+		b = h
+	} while (b != 0)
+	return abs(a)
+}
+
+function cancel(f: [number, number]) {
+	let [a, b] = f
+	let d: number
+	do {
+		d = gcd(a, b)
+		a /= d
+		b /= d
+	} while (d !== 1)
+	return [a, b]
+}
+
+//const input = ".#....#####...#..\n##...##.#####..##\n##...#...#.#####.\n..#.....X...###..\n..#.#.....#....##"
+const input = fs.readFileSync("input-day10.txt", "utf8")
+
+const image = flip(input
+	.split("\n")
+	.map(l => l.split("")))
+
+const w = image.length
+const h = image[0].length
+
+const ds = new Set<string>()
+for (let x = -w + 1; x < w; x++) {
+	for (let y = -h + 1; y < h; y++) {
+		if (x === 0 && y === 0) {
+			continue
+		}
+		ds.add(JSON.stringify(cancel([x, y])))
+	}
+}
+
+const dirs = Array.from(ds).map(d => JSON.parse(d) as [number, number])
+	.map(d => [...d, Math.atan2(d[1], d[0]) * 180 / Math.PI - 270])
+	.map(d => [d[0], d[1], (2 * 360 + d[2]) % 360])
+	.sort((a, b) => a[2] - b[2])
+	.map(d => [d[0], d[1]] as const)
+
+function shoot(x: number, y: number, d: readonly [number, number]): [number, number] | undefined {
+	do {
+		x += d[0]
+		y += d[1]
+		if (x < 0 || x >= w) {
+			return undefined
+		}
+		if (y < 0 || y >= h) {
+			return undefined
+		}
+		if (image[x][y] == "#") {
+			image[x][y] = "x"
+			return [x, y]
+		}
+	} while (true)
+}
+
+let p = [17, 23]
+//let p = [8, 3]
+let count = 0
+let i = 0
+
+while (true) {
+	const d = dirs[i++ % dirs.length]
+	const shot = shoot(p[0], p[1], d)
+	if (shot) {
+		count++
+		print(image)
+	}
+	if (count == 200) {
+		console.log(shot)
+		console.log("---")
+		break
+	}
+}
+

day10.ts

@@ -0,0 +1,100 @@
+import * as fs from "fs"
+
+const abs = Math.abs
+
+function flip<T>(a: T[][]) {
+	const flipped = Array.from(Array(a[0].length)).map(() => Array.from(Array(a.length)))
+	for (let x = 0; x < flipped.length; x++) {
+		for (let y = 0; y < flipped[0].length; y++) {
+			flipped[x][y] = a[y][x]
+		}
+	}
+	return flipped
+}
+
+function print<T>(a: T[][]) {
+	for (let y = 0; y < a[0].length; y++) {
+		console.log(Array(a.length).fill(0).map((_, x) => a[x][y]).join(""))
+	}
+}
+
+function gcd(a: number, b: number) {
+	if (a == 0) return abs(b)
+	if (b == 0) return abs(a)
+
+	let h: number
+	do {
+		h = a % b
+		a = b
+		b = h
+	} while (b != 0)
+	return abs(a)
+}
+
+function cancel(f: [number, number]) {
+	let [a, b] = f
+	let d: number
+	do {
+		d = gcd(a, b)
+		a /= d
+		b /= d
+	} while (d !== 1)
+	return [a, b]
+}
+
+const input = fs.readFileSync("input-day10.txt", "utf8")
+
+const image = flip(input
+	.split("\n")
+	.map(l => l.split("")))
+
+const w = image.length
+const h = image[0].length
+
+const ds = new Set<string>()
+for (let x = -w + 1; x < w; x++) {
+	for (let y = -h + 1; y < h; y++) {
+		if (x === 0 && y === 0) {
+			continue
+		}
+		ds.add(JSON.stringify(cancel([x, y])))
+	}
+}
+
+const dirs = Array.from(ds).map(d => JSON.parse(d))
+
+function count(x: number, y: number): number {
+	if (image[x][y] != "#") {
+		return 0
+	}
+
+	return dirs.map(d => countDir(x, y, d)).reduce((a, v) => a + v, 0)
+}
+
+function countDir(x: number, y: number, d: [number, number]): number {
+	do {
+		x += d[0]
+		y += d[1]
+		if (x < 0 || x >= w) {
+			return 0
+		}
+		if (y < 0 || y >= h) {
+			return 0
+		}
+		if (image[x][y] == "#") {
+			return 1
+		}
+	} while (true)
+}
+
+let best = [0, -1, -1]
+for (let x = 0; x < w; x++) {
+	for (let y = 0; y < h; y++) {
+		const c = count(x, y)
+		if (c > best[0]) {
+			best = [c, x, y]
+		}
+	}
+}
+print(image)
+console.log(best)

input-day10.txt

@@ -0,0 +1,27 @@
+.###..#######..####..##...#
+########.#.###...###.#....#
+###..#...#######...#..####.
+.##.#.....#....##.#.#.....#
+###.#######.###..##......#.
+#..###..###.##.#.#####....#
+#.##..###....#####...##.##.
+####.##..#...#####.#..###.#
+#..#....####.####.###.#.###
+#..#..#....###...#####..#..
+##...####.######....#.####.
+####.##...###.####..##....#
+#.#..#.###.#.##.####..#...#
+..##..##....#.#..##..#.#..#
+##.##.#..######.#..#..####.
+#.....#####.##........#####
+###.#.#######..#.#.##..#..#
+###...#..#.#..##.##..#####.
+.##.#..#...#####.###.##.##.
+...#.#.######.#####.#.####.
+#..##..###...###.#.#..#.#.#
+.#..#.#......#.###...###..#
+#.##.#.#..#.#......#..#..##
+.##.##.##.#...##.##.##.#..#
+#.###.#.#...##..#####.###.#
+#.####.#..#.#.##.######.#..
+.#.#####.##...#...#.##...#.