Day04a: Solved

lib/day04.dart

@@ -0,0 +1,40 @@
+// --- Day 4: Scratchcards ---
+// https://adventofcode.com/2023/day/4
+
+import 'package:collection/collection.dart';
+
+int solveA(Iterable<String> input) => input
+    .map(parse)
+    .map((card) =>
+        1 << card.winningNumbers.intersection(card.numbersYouHave).length >> 1)
+    .sum;
+
+int solveB(Iterable<String> input) {
+  return 0;
+}
+
+RegExp regExp = RegExp(r'Card +(\d+): (.*) \| (.*)');
+
+({
+  int cardId,
+  Set<int> winningNumbers,
+  Set<int> numbersYouHave,
+}) parse(String line) {
+  final match = regExp.firstMatch(line)!;
+
+  return (
+    cardId: int.parse(match[1]!),
+    winningNumbers: match[2]!
+        .split(' ')
+        .map((e) => e.trim())
+        .where((e) => e.isNotEmpty)
+        .map(int.parse)
+        .toSet(),
+    numbersYouHave: match[3]!
+        .split(' ')
+        .map((e) => e.trim())
+        .where((e) => e.isNotEmpty)
+        .map(int.parse)
+        .toSet(),
+  );
+}