feat(day-7): add first part solution

1 files changed, 72 insertions, 0 deletions

diff --git a/day-7/script.ts b/day-7/script.ts
new file mode 100644
index 0000000..0d812f7
--- /dev/null
+++ b/day-7/script.ts
@@ -0,0 +1,72 @@
+import fs from "fs";
+
+enum HandType {
+  highCard,
+  onePair,
+  twoPair,
+  threeOfAKind,
+  fullHouse,
+  fourOfAKind,
+  fiveOfAKind,
+}
+
+const cardStrength = [
+  "2",
+  "3",
+  "4",
+  "5",
+  "6",
+  "7",
+  "8",
+  "9",
+  "T",
+  "J",
+  "Q",
+  "K",
+  "A",
+];
+
+function classifyHand(hand: string) {
+  const cards = hand.split("");
+  const counts = Array.from(new Set(cards))
+    .map((card) => cards.filter((c) => c === card).length)
+    .sort()
+    .reverse();
+
+  if (counts[0] === 5) return HandType.fiveOfAKind;
+  if (counts[0] === 4) return HandType.fourOfAKind;
+  if (counts[0] === 3 && counts[1] === 2) return HandType.fullHouse;
+  if (counts[0] === 3) return HandType.threeOfAKind;
+  if (counts[0] === 2 && counts[1] === 2) return HandType.twoPair;
+  if (counts[0] === 2) return HandType.onePair;
+  return HandType.highCard;
+}
+
+const input = fs
+  .readFileSync("./input.txt")
+  .toString()
+  .split("\n")
+  .slice(0, -1)
+  .map((line) => {
+    const match = line.match(/(.....) (\d+)/);
+    if (!match) throw new Error("Unexpected format");
+    return {
+      hand: match[1],
+      bid: Number(match[2]),
+      type: classifyHand(match[1]),
+    };
+  })
+  .sort((a, b) => {
+    const diff = a.type - b.type;
+    if (diff) return diff;
+
+    return [0, 1, 2, 3, 4].reduce((acc, index) => {
+      return acc
+        ? acc
+        : cardStrength.indexOf(a.hand[index]) -
+            cardStrength.indexOf(b.hand[index]);
+    }, 0);
+  })
+  .reduce((sum, item, index) => sum + item.bid * (index + 1), 0);
+
+console.log({ input });