2024 day 8

2024/day-8/day8.ts

@@ -0,0 +1,186 @@
+export function part1(input: string) {
+	const lines = input.split("\n");
+	const height = lines.length;
+	const width = lines[0].length;
+	const antennas = new Map();
+	for (let i = 0; i < lines.length; i++) {
+		const line = lines[i];
+		for (let j = 0; j < line.length; j++) {
+			const char = line[j];
+			if (char === ".") {
+				continue;
+			}
+			const [x, y] = [i, j];
+			if (antennas.has(char)) {
+				const current = antennas.get(char);
+
+				current.push([x, y]);
+			} else {
+				antennas.set(char, [[x, y]]);
+			}
+		}
+	}
+
+	const antinodes = [];
+	for (const frequency of antennas.keys()) {
+		const antennasOnFreq = antennas.get(frequency);
+		for (let i = 0; i < antennasOnFreq.length; i++) {
+			for (let j = i + 1; j < antennasOnFreq.length; j++) {
+				const p1 = antennasOnFreq[i];
+				const p2 = antennasOnFreq[j];
+				const distanceX = Math.abs(p1[0] - p2[0]);
+				const distanceY = Math.abs(p1[1] - p2[1]);
+				const antinode1 = [];
+				const antinode2 = [];
+
+				if (p1[0] > p2[0]) {
+					antinode1[0] = p1[0] + distanceX;
+					antinode2[0] = p2[0] - distanceX;
+				} else {
+					antinode1[0] = p1[0] - distanceX;
+					antinode2[0] = p2[0] + distanceX;
+				}
+
+				if (p1[1] > p2[1]) {
+					antinode1[1] = p1[1] + distanceY;
+					antinode2[1] = p2[1] - distanceY;
+				} else {
+					antinode1[1] = p1[1] - distanceY;
+					antinode2[1] = p2[1] + distanceY;
+				}
+				if (
+					!(
+						antinode1[0] < 0 ||
+						antinode1[0] >= height ||
+						antinode1[1] < 0 ||
+						antinode1[1] >= width
+					)
+				) {
+					antinodes.push(antinode1);
+				}
+				if (
+					!(
+						antinode2[0] < 0 ||
+						antinode2[0] >= height ||
+						antinode2[1] < 0 ||
+						antinode2[1] >= width
+					)
+				) {
+					antinodes.push(antinode2);
+				}
+			}
+		}
+	}
+	const uniqueAntinodes = [...new Set(antinodes.map((x) => x.join(",")))].map(
+		(x) => x.split(","),
+	);
+
+	return uniqueAntinodes.length;
+}
+
+export function part2(input: string) {
+	const lines = input.split("\n");
+	const height = lines.length;
+	const width = lines[0].length;
+	const antennas = new Map();
+	for (let i = 0; i < lines.length; i++) {
+		const line = lines[i];
+		for (let j = 0; j < line.length; j++) {
+			const char = line[j];
+			if (char === ".") {
+				continue;
+			}
+			const [x, y] = [i, j];
+			if (antennas.has(char)) {
+				const current = antennas.get(char);
+
+				current.push([x, y]);
+			} else {
+				antennas.set(char, [[x, y]]);
+			}
+		}
+	}
+
+	const antinodes: [number, number][] = [];
+	for (const frequency of antennas.keys()) {
+		const antennasOnFreq = antennas.get(frequency);
+		for (let i = 0; i < antennasOnFreq.length; i++) {
+			for (let j = i + 1; j < antennasOnFreq.length; j++) {
+				const p1 = antennasOnFreq[i];
+				const p2 = antennasOnFreq[j];
+				const distanceX = Math.abs(p1[0] - p2[0]);
+				const distanceY = Math.abs(p1[1] - p2[1]);
+				antinodes.push(p1, p2);
+				if (p1[0] < p2[0] && p1[1] < p2[1]) {
+					let nextX = p2[0];
+					let nextY = p2[1];
+					while (true) {
+						nextX = nextX + distanceX;
+						nextY = nextY + distanceY;
+
+						if (nextX >= 0 && nextX < height && nextY >= 0 && nextY < width) {
+							antinodes.push([nextX, nextY]);
+						} else {
+							break;
+						}
+					}
+					let prevX = p2[0];
+					let prevY = p2[1];
+					while (true) {
+						prevX = prevX - distanceX;
+						prevY = prevY - distanceY;
+
+						if (prevX >= 0 && prevX < height && prevY >= 0 && prevY < width) {
+							antinodes.push([prevX, prevY]);
+						} else {
+							break;
+						}
+					}
+				} else if (p1[0] < p2[0] && p1[1] > p2[1]) {
+					let nextX = p2[0];
+					let nextY = p2[1];
+					while (true) {
+						nextX = nextX - distanceX;
+						nextY = nextY + distanceY;
+
+						if (nextX >= 0 && nextX < height && nextY >= 0 && nextY < width) {
+							antinodes.push([nextX, nextY]);
+						} else {
+							break;
+						}
+					}
+					let prevX = p2[0];
+					let prevY = p2[1];
+					while (true) {
+						prevX = prevX + distanceX;
+						prevY = prevY - distanceY;
+
+						if (prevX >= 0 && prevX < height && prevY >= 0 && prevY < width) {
+							antinodes.push([prevX, prevY]);
+						} else {
+							break;
+						}
+					}
+				}
+			}
+		}
+	}
+	const uniqueAntinodes = [...new Set(antinodes.map((x) => x.join(",")))].map(
+		(x) => x.split(","),
+	);
+
+	// display(lines, uniqueAntinodes);
+
+	return uniqueAntinodes.length;
+}
+
+function display(lines: string[], antinodes: string[][]) {
+	const nl = lines.map((x) => x.split(""));
+
+	for (const u of antinodes) {
+		nl[u[0]][u[1]] === "." ? (nl[u[0]][u[1]] = "#") : null;
+	}
+	for (const x of nl) {
+		console.log(x.join(""));
+	}
+}