AoC-23/Day9/Part2.js

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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();
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let extrapolated = [last[0], ...last];
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for (const s of sequences.reverse()) {
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const current = s.shift();
const last = extrapolated.shift();
extrapolated = [current - last, ...s];
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}
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return extrapolated.shift();
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});
const sum = predictions.reduce((a, i) => a + i);
console.log(sum);
const t1 = performance.now();
console.log(`Runtime: ${t1 - t0}ms`);