add day 9 solution

09/a.test.ts

@@ -0,0 +1,53 @@
+import { expect, test } from "bun:test";
+
+function solution(input: string) {
+    const sequences = input.split("\n").map((line) => line.split(" ").map(Number));
+
+    let ans = 0;
+
+    for (const sequence of sequences) {
+        const acc = [sequence];
+
+        let last = acc[acc.length - 1];
+        while (!last.every((el) => el === 0)) {
+            const next = [];
+            for (let i = 1; i < last.length; i++) {
+                const el = last[i] - last[i - 1];
+                next.push(el);
+            }
+            acc.push(next);
+            last = next;
+        }
+
+        const acc1 = acc.map((el) => el[el.length - 1]);
+        const acc2 = [0];
+
+        for (let i = acc1.length - 2; i >= 0; i--) {
+            const next = acc1[i] + acc2[acc2.length - 1];
+            acc2.push(next);
+        }
+
+        ans += acc2[acc2.length - 1];
+    }
+
+    return ans;
+}
+
+test("example", async () => {
+    const file = Bun.file(`${import.meta.dir}/example.txt`);
+    const input = await file.text();
+
+    const actual = solution(input);
+    const expected = 114;
+    expect(actual).toBe(expected);
+});
+
+test("puzzle input", async () => {
+    const file = Bun.file(`${import.meta.dir}/input.txt`);
+    const input = await file.text();
+
+    const actual = solution(input);
+    const expected = 1702218515;
+
+    expect(actual).toBe(expected);
+});

09/b.test.ts

@@ -0,0 +1,53 @@
+import { expect, test } from "bun:test";
+
+function solution(input: string) {
+    const sequences = input.split("\n").map((line) => line.split(" ").map(Number));
+
+    let ans = 0;
+
+    for (const sequence of sequences) {
+        const acc = [sequence];
+
+        let last = acc[acc.length - 1];
+        while (!last.every((el) => el === 0)) {
+            const next = [];
+            for (let i = 1; i < last.length; i++) {
+                const el = last[i] - last[i - 1];
+                next.push(el);
+            }
+            acc.push(next);
+            last = next;
+        }
+
+        const acc1 = acc.map((el) => el[0]);
+        const acc2 = [0];
+
+        for (let i = acc1.length - 2; i >= 0; i--) {
+            const next = acc1[i] - acc2[acc2.length - 1];
+            acc2.push(next);
+        }
+
+        ans += acc2[acc2.length - 1];
+    }
+
+    return ans;
+}
+
+test("example", async () => {
+    const file = Bun.file(`${import.meta.dir}/example.txt`);
+    const input = await file.text();
+
+    const actual = solution(input);
+    const expected = 2;
+    expect(actual).toBe(expected);
+});
+
+test("puzzle input", async () => {
+    const file = Bun.file(`${import.meta.dir}/input.txt`);
+    const input = await file.text();
+
+    const actual = solution(input);
+    const expected = 925;
+
+    expect(actual).toBe(expected);
+});

09/example.txt

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+0 3 6 9 12 15
+1 3 6 10 15 21
+10 13 16 21 30 45