From 1c7c8bab4dd52e53924ef0bf75834f67b4fdacf0 Mon Sep 17 00:00:00 2001
From: Timothy Quilling <teqed@shatteredsky.net>
Date: Fri, 15 Dec 2023 21:12:02 -0500
Subject: [PATCH] Day 4

---
 src/day4/typescript/main.test.ts | 29 +++++++++++++++
 src/day4/typescript/main.ts      | 62 ++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+)
 create mode 100644 src/day4/typescript/main.test.ts
 create mode 100644 src/day4/typescript/main.ts

diff --git a/src/day4/typescript/main.test.ts b/src/day4/typescript/main.test.ts
new file mode 100644
index 0000000..6be504c
--- /dev/null
+++ b/src/day4/typescript/main.test.ts
@@ -0,0 +1,29 @@
+/* eslint-disable @typescript-eslint/no-unsafe-call */
+import {readFileSync} from 'node:fs';
+import {assertEquals} from 'https://deno.land/std@0.209.0/assert/mod.ts';
+import {assertLess} from 'https://deno.land/std@0.209.0/assert/assert_less.ts';
+import {partA, partB} from './main.ts'; // eslint-disable-line n/file-extension-in-import
+
+const day = 4;
+const answerExample = 13;
+const answerA = 22_193;
+const answerB = 5_625_994;
+const answerExampleB = 30;
+const input: string[] = readFileSync(`src/day${day}/input.txt`, 'utf8').split('\n');
+const inputExample: string[] = readFileSync(`src/day${day}/input_example.txt`, 'utf8').split('\n');
+
+Deno.test('Example', () => {
+	assertEquals(partA(inputExample), answerExample);
+});
+
+Deno.test('Part A', () => {
+	assertEquals(partA(input), answerA);
+});
+
+Deno.test('Example B', () => {
+	assertEquals(partB(inputExample), answerExampleB);
+});
+
+Deno.test('Part B', () => {
+	assertEquals(partB(input), answerB);
+});
diff --git a/src/day4/typescript/main.ts b/src/day4/typescript/main.ts
new file mode 100644
index 0000000..96f8989
--- /dev/null
+++ b/src/day4/typescript/main.ts
@@ -0,0 +1,62 @@
+export const partA = (input: string[]) => {
+	let totalPoints = 0;
+
+	for (const card of input) {
+		const _card = card.slice(card.indexOf(':') + 1).trim();
+		const [winningNumbers, yourNumbers] = _card.split('|').map(numbers => numbers.trim().split(/\s+/).map(Number));
+		const matches = yourNumbers.filter(number => winningNumbers.includes(number)).length;
+		totalPoints += matches > 0 ? 2 ** (matches - 1) : 0;
+	}
+
+	return totalPoints;
+};
+
+export const partB = (input: string[]) => {
+	// Let's create a dictionary of matches, so we can easily find it on repeated cards.
+	type Card = {
+		cardNumber: number;
+		winningNumbers: number[];
+		yourNumbers: number[];
+		matches: number;
+		additionalCards?: number[];
+		card: string;
+	};
+	const cards: Card[] = [];
+	for (const card of input) {
+		const cardNumber = input.indexOf(card) + 1;
+		const _card = card.slice(card.indexOf(':') + 1).trim();
+		const [winningNumbers, yourNumbers] = _card.split('|').map(numbers => numbers.trim().split(/\s+/).map(Number));
+		const matches = yourNumbers.filter(number => winningNumbers.includes(number)).length;
+		const additionalCards = matches > 0 ? Array.from({length: matches}, (_, i) => cardNumber + i + 1) : undefined;
+		cards.push({cardNumber, winningNumbers, yourNumbers, matches, additionalCards, card});
+	}
+
+	let totalCards = 0;
+
+	type CardBinder = {
+		card: Card;
+		count: number;
+	};
+	const cardBinders: Record<number, CardBinder> = {};
+	for (const card of cards) {
+		cardBinders[card.cardNumber] = {card, count: 1};
+	}
+
+	for (const binder of Object.values(cardBinders)) {
+		if (binder.card.matches === 0) {
+			continue;
+		} else if (binder.card.matches > 0) {
+			for (const cardNumber of binder.card.additionalCards!) {
+				cardBinders[cardNumber].count += Number(binder.count);
+			}
+		}
+	}
+
+	for (const binder of Object.values(cardBinders)) {
+		totalCards += binder.count;
+	}
+
+	console.log(`Total cards: ${totalCards}`);
+
+	return totalCards;
+};
-- 
2.51.2