day 2

day-2/day2.ts

@@ -0,0 +1,76 @@
+export async function day2(input: string) {
+	const lines = input.split("\n");
+	let count = 0;
+	for (const line of lines) {
+		const levels = line.split(" ").map((v) => Number.parseInt(v, 10));
+		const safe = isSafe(levels);
+
+		if (safe) {
+			count++;
+		}
+	}
+	return count;
+}
+
+export async function day2part2(input: string) {
+	const lines = input.split("\n");
+	let count = 0;
+	for (const line of lines) {
+		const levels = line.split(" ").map((v) => Number.parseInt(v, 10));
+		const isFullySafe = isSafe(levels);
+
+		if (isFullySafe) {
+			count++;
+			continue;
+		}
+
+		let isDampenedSafe = false;
+
+		for (let i = 0; i < levels.length; i++) {
+			const toTry = levels.toSpliced(i, 1);
+
+			if (isSafe(toTry)) {
+				isDampenedSafe = true;
+				break;
+			}
+		}
+
+		if (isDampenedSafe) {
+			count++;
+		}
+	}
+
+	return count;
+}
+
+function isSafe(levels: number[]) {
+	let increasing = null;
+	let safe = true;
+
+	for (let i = 0; i < levels.length - 1; i++) {
+		const current = levels[i];
+		const next = levels[i + 1];
+		const diff = Math.abs(next - current);
+
+		if (diff > 3 || diff < 1) {
+			safe = false;
+			break;
+		}
+
+		if (i === 0) {
+			increasing = next > current;
+			continue;
+		}
+
+		if (increasing && next <= current) {
+			safe = false;
+			break;
+		}
+
+		if (!increasing && next >= current) {
+			safe = false;
+			break;
+		}
+	}
+	return safe;
+}