add 9

9.2.ts

@@ -0,0 +1,31 @@
+import { open } from 'node:fs/promises';
+
+function computeDifference(input: number[]) {
+    const output: number[] = []
+    input.forEach((e, i, arr) => {
+        if (i === 0) return
+        output.push(arr[i] - arr[i - 1])
+    });
+    return output
+}
+const file = await open('./inputs/9');
+let sum = 0
+for await (const line of file.readLines()) {
+    const numbers = line.split(" ").map<number>(e => Number(e))
+    const differences: number[][] = [numbers]
+    if (differences.at(-1) === undefined) throw new Error('wtf')
+
+    while (!differences.at(-1)?.every(e => e === 0)) {
+        differences.push(computeDifference(differences.at(-1)!))
+    }
+
+
+    let acc = differences.reduceRight((prev, cur) => {
+        cur.unshift(cur.at(0)! - prev)
+        return cur.at(0)!
+    }, 0)
+    sum += acc
+}
+console.log(sum)
+
+