feat(day-9): add first part solution

1 files changed, 26 insertions, 0 deletions

diff --git a/day-9/script.ts b/day-9/script.ts
new file mode 100644
index 0000000..cb1ac38
--- /dev/null
+++ b/day-9/script.ts
@@ -0,0 +1,26 @@
+import fs from "fs";
+
+function differences(sequence: number[]) {
+  return sequence.reduce((acc, value, index) => {
+    const next = sequence[index + 1];
+    if (next !== undefined) acc.push(next - value);
+    return acc;
+  }, [] as number[]);
+}
+
+function predictValue(sequence: number[]) {
+  if (sequence.every((item) => item === 0)) return 0;
+  const diff = predictValue(differences(sequence));
+  return sequence[sequence.length - 1] + diff;
+}
+
+const result = fs
+  .readFileSync("./input.txt")
+  .toString()
+  .split("\n")
+  .slice(0, -1)
+  .map((line) => line.split(" ").map(Number))
+  .map(predictValue)
+  .reduce((sum, value) => sum + value, 0);
+
+console.log({ result });