day 13 part 1

AdventOfCode/Day13.cs

@@ -0,0 +1,103 @@
+using System.Text.RegularExpressions;
+
+namespace AdventOfCode;
+
+public class Day13 : BaseDay
+{
+    private readonly List<ClawMachine> _clawMachines = new List<ClawMachine>();
+
+    public Day13() 
+    {
+        string[] lines = File.ReadAllLines(InputFilePath);
+
+        Button? a = null, b = null;
+        Prize prize;
+        foreach (string line in lines)
+        {
+            if (string.IsNullOrWhiteSpace(line))
+            {
+                continue;
+            }
+            if (line.StartsWith("Button"))
+            {
+                Match match = Regex.Match(line, "Button (A|B): X\\+([0-9]+), Y\\+([0-9]+)");
+                int x = int.Parse(match.Groups[2].Value);
+                int y = int.Parse(match.Groups[3].Value);
+                Button button = new Button(x, y);
+                if (match.Groups[1].Value == "A")
+                {
+                    a = button;
+                }
+                else
+                {
+                    b = button;
+                }
+            }
+            else if (line.StartsWith("Prize"))
+            {
+                Match match = Regex.Match(line, "Prize: X=([0-9]+), Y=([0-9]+)");
+                int x = int.Parse(match.Groups[1].Value);
+                int y = int.Parse(match.Groups[2].Value);
+                prize = new Prize(x, y);
+
+                _clawMachines.Add(new ClawMachine(a!, b!, prize));
+            }
+        }
+    }
+
+    public override ValueTask<string> Solve_1()
+    {
+        int price = 0;
+        foreach (var clawMachine in _clawMachines)
+        {
+            (int? aMoves, int? bMoves) = GetSolution(clawMachine);
+            if (aMoves.HasValue && bMoves.HasValue)
+            {
+                price += GetPrice(aMoves.Value, bMoves.Value);
+            }
+        }
+
+        return new(price.ToString());
+    }
+
+    public override ValueTask<string> Solve_2()
+    {
+        return new("");
+    }
+
+    private (int? aMoves, int? bMoves) GetSolution(ClawMachine c)
+    {
+         bool bSolutionExists = (c.ButtonA.Y * c.Prize.X - c.Prize.Y * c.ButtonA.X) 
+            % (c.ButtonA.Y * c.ButtonB.X - c.ButtonA.X * c.ButtonB.Y) == 0;
+
+        if (!bSolutionExists)
+        {
+            return (null, null);
+        }
+
+        int bMoves = (c.ButtonA.Y * c.Prize.X - c.Prize.Y * c.ButtonA.X)
+            / (c.ButtonA.Y * c.ButtonB.X - c.ButtonA.X * c.ButtonB.Y);
+
+        bool aSolutionExists = (c.Prize.Y - c.ButtonB.Y * bMoves) % c.ButtonA.Y == 0;
+
+        if (!aSolutionExists)
+        {
+            return (null, null);
+        }
+
+        int aMoves = (c.Prize.Y - c.ButtonB.Y * bMoves) / c.ButtonA.Y;
+
+        return (aMoves, bMoves);
+    }
+
+    private int GetPrice(int aMoves, int bMoves)
+    { 
+        return aMoves * 3 + bMoves;
+    }
+
+    private record Button(int X, int Y);
+
+    private record Prize(int X, int Y);
+
+    private record ClawMachine(Button ButtonA, Button ButtonB, Prize Prize);
+}