1 files changed, 59 insertions, 0 deletions
diff --git a/day-12/sol.ts b/day-12/sol.ts
new file mode 100644
index 0000000..7143403
--- /dev/null
+++ b/day-12/sol.ts
@@ -0,0 +1,59 @@
+import * as input from "fs";
+
+type NestedNumbers = Array<NestedNumbers | number>;
+
+const compare = (
+  a: NestedNumbers | number,
+  b: NestedNumbers | number
+): boolean => {
+  if (typeof a === typeof b && typeof b === "number") return a < b;
+  if (Array.isArray(a) && Array.isArray(b)) {
+    for (let i = 0; i < a.length; i++) {
+      if (i >= b.length) return false;
+      if (compare(a[i], b[i])) return true;
+      if (compare(b[i], a[i])) return false;
+    }
+    return compare(a.length, b.length);
+  }
+  return compare(Array.isArray(b) ? [a] : a, Array.isArray(a) ? [b] : b);
+};
+
+const main = (): void => {
+  const lines: NestedNumbers[] = input
+    .readFileSync("input", "utf-8")
+    .split("\n")
+    .filter((x) => x)
+    .map((x) => JSON.parse(x));
+
+  const pairs: [NestedNumbers, NestedNumbers][] = [];
+  for (let i = 0; i < lines.length; i += 2) {
+    const pair: [NestedNumbers, NestedNumbers] = [lines[i], lines[i + 1]];
+    pairs.push(pair);
+  }
+
+  console.log(
+    pairs.reduce((acc, [a, b], i) => acc + (compare(a, b) ? i + 1 : 0), 0)
+  );
+
+  lines.push([[2]]);
+  lines.push([[6]]);
+
+  const sorted = lines.sort((a, b) => {
+    if (compare(a, b)) return -1;
+    if (compare(b, a)) return 1;
+    return 0;
+  });
+
+  const isPacket = (num: number) => (x: NestedNumbers) =>
+    Array.isArray(x) &&
+    x.length === 1 &&
+    Array.isArray(x[0]) &&
+    x[0].length === 1 &&
+    x[0][0] === num;
+
+  console.log(
+    (sorted.findIndex(isPacket(6)) + 1) * (sorted.findIndex(isPacket(2)) + 1)
+  );
+};
+
+main();