Day 4 solutions 😶😶

day_4/part_1.ts

@@ -0,0 +1,27 @@
+import * as fs from "fs";
+
+const input = fs.readFileSync("input", "utf8");
+
+const cards = input.split("\n").map((card) =>
+  card
+    .split(": ")[1]
+    .split(" | ")
+    .map((part) =>
+      part
+        .split(" ")
+        .filter((num) => num !== "")
+        .map((num) => parseInt(num))
+    )
+);
+
+console.log(
+  cards
+    .map((card) =>
+      card[1].reduce(
+        (score, your_number) =>
+          card[0].includes(your_number) ? (score === 0 ? 1 : score * 2) : score,
+        0
+      )
+    )
+    .reduce((sum, score) => sum + score, 0)
+);

day_4/part_2.ts

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+import * as fs from "fs";
+
+const input = fs.readFileSync("input", "utf8");
+
+const cards = input.split("\n").map((card) =>
+  card
+    .split(": ")[1]
+    .split(" | ")
+    .map((part) =>
+      part
+        .split(" ")
+        .filter((num) => num !== "")
+        .map((num) => parseInt(num))
+    )
+);
+
+const card_dupe_count = Array(cards.length).fill(1);
+
+const get_matching_numbers = (card: number[][]) =>
+  card[1].reduce(
+    (score, your_number) => (card[0].includes(your_number) ? score + 1 : score),
+    0
+  );
+
+cards.map((card, i) => {
+  const matching_numbers = get_matching_numbers(card);
+  [...Array(matching_numbers).keys()].forEach((off) => {
+    card_dupe_count[i + off + 1] += card_dupe_count[i];
+  });
+});
+
+console.log(card_dupe_count.reduce((sum, v) => sum + v, 0));