2023 Day 2

src/2023/02/Program.cs

@@ -1,3 +1,45 @@
-using AdventOfCode.Common;
+using System.Text.RegularExpressions;
+using AdventOfCode.Common;
 
-var lines = Resources.GetInputFileLines();
+// Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
+var inputRegex = new Regex("Game (?<gameId>\\d+):");
+var revealRegex = new Regex("(?<count>\\d+) (?<color>blue|red|green)");
+var games = new List<Game>();
+
+foreach (var line in Resources.GetInputFileLines())
+{
+    var id = int.Parse(inputRegex.Match(line).Groups["gameId"].Value);
+    var reveals = line
+        .SplitBy(";")
+        .Select(reveals => revealRegex.Matches(reveals))
+        .Select(reveals => reveals.Select(reveal =>
+            (Count: int.Parse(reveal.Groups["count"].Value),
+             Color: reveal.Groups["color"].Value)))
+        .Select(reveals => new Reveal(
+            Red: reveals.FirstOrDefault(r => r.Color == "red").Count,
+            Blue: reveals.FirstOrDefault(r => r.Color == "blue").Count,
+            Green: reveals.FirstOrDefault(r => r.Color == "green").Count))
+        .ToList();
+
+    games.Add(new Game(id, reveals));
+}
+
+var part1Bag = new Reveal(Red: 12, Green: 13, Blue: 14);
+var possibleGames = games
+    .Where(game => game.Reveals.All(reveal =>
+        reveal.Red <= part1Bag.Red &&
+        reveal.Green <= part1Bag.Green &&
+        reveal.Blue <= part1Bag.Blue));
+
+var leastCubes = games
+    .Select(game => new Reveal(
+        Red: game.Reveals.Max(reveal => reveal.Red),
+        Green: game.Reveals.Max(reveal => reveal.Green),
+        Blue: game.Reveals.Max(reveal => reveal.Blue)))
+    .Select(leastCubes => leastCubes.Red * leastCubes.Blue * leastCubes.Green);
+
+Console.WriteLine($"Part 1: {possibleGames.Select(game => game.Id).Sum()}");
+Console.WriteLine($"Part 2: {leastCubes.Sum()}");
+
+file record Reveal(int Blue, int Red, int Green);
+file record Game(int Id, IReadOnlyCollection<Reveal> Reveals);