From 5cf420dc2650e9a3155699e7be9284b25baee406 Mon Sep 17 00:00:00 2001
From: Baipyrus <simon.waltemathe@gmail.com>
Date: Sat, 9 Dec 2023 22:31:48 +0100
Subject: [PATCH] init d9p2

---
 Day9/Part2.js | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
 create mode 100644 Day9/Part2.js

diff --git a/Day9/Part2.js b/Day9/Part2.js
new file mode 100644
index 0000000..6782614
--- /dev/null
+++ b/Day9/Part2.js
@@ -0,0 +1,35 @@
+import { readFileSync } from "fs";
+const t0 = performance.now();
+
+const input = readFileSync("input.txt")
+	.toString()
+	.split("\n")
+	.filter((e) => e.length > 0);
+const histories = input.map((e) => e.split(" ").map(Number));
+const predictions = histories.map((e) => {
+	let current = e;
+	const sequences = [];
+	while (!current.every((e) => e === 0)) {
+		sequences.push(current);
+		current = current.reduce((a, n, i) => {
+			if (i === 0) return a;
+			const d = n - current[i - 1];
+			const t = a;
+			t.push(d);
+			return t;
+		}, []);
+	}
+	const last = sequences.pop();
+	const extrapolated = [[...last, last[0]]];
+	for (const s of sequences.reverse()) {
+		const current = s.pop();
+		const last = extrapolated.pop().pop();
+		extrapolated.push([...s, current + last]);
+	}
+	return extrapolated.pop().pop();
+});
+const sum = predictions.reduce((a, i) => a + i);
+console.log(sum);
+
+const t1 = performance.now();
+console.log(`Runtime: ${t1 - t0}ms`);