Day 7 Part1

Day 8

AdventOfCode/Problems/AOC2024/Day6/GuardGallivant.cs

@@ -204,7 +204,6 @@ internal class GuardGallivant : Problem<int, int>
 					found.Add(obstaclePos);
 
 				}
-				//}
 			}
 		}
 	}
@@ -253,13 +252,13 @@ file class GuardMap
 		var curNode = nodes[0];
 		while (true)
 		{
-			if (curNode.Next is int nextId)
+			if (curNode.Next is int nextId && nextId >= 0)
 			{
 				var next = nodes[nextId];
 				path.AddRange(GetPointsBetween(curNode.Pos, next.Pos, curNode.Direction).Select(p => (p, curNode)));
 				curNode = next;
 			}
-			else
+			else if(curNode.Next == -1)
 			{
 				var end = curNode.Direction switch
 				{
@@ -271,7 +270,8 @@ file class GuardMap
 				};
 				path.AddRange(GetPointsBetween(curNode.Pos, end, curNode.Direction).Select(p => (p, curNode)));
 				break;
-			}
+			}else
+				break;
 		}
 
 		return path;
@@ -312,7 +312,11 @@ file class GuardMap
 		while (true)
 		{
 			if (!GetNextObstacle(curNode.Pos, curNode.Direction, out var next))
+			{
+				curNode.Next = -1;
+				Nodes[curNode.Id] = curNode;
 				break;
+			}
 			var newNode = new GuardNode(next - GuardGallivant.DIRS[curNode.Direction], (curNode.Direction + 1) % 4, Nodes.Count);
 			curNode.Next = newNode.Id;
 			Nodes[curNode.Id] = curNode;

AdventOfCode/Problems/AOC2024/Day7/BridgeRepair.cs

@@ -5,6 +5,70 @@ using System.Text;
 using System.Threading.Tasks;
 
 namespace AdventOfCode.Problems.AOC2024.Day7;
-internal class BridgeRepair
+
+[ProblemInfo(2024, 7, "Bridge Repair")]
+internal class BridgeRepair : Problem<ulong, ulong>
 {
-}
+	private List<(ulong total, ulong[] nums)> _data = [];
+
+	private enum Operator
+	{
+		Mul,
+		Add,
+		Concat
+	}
+
+	public override void CalculatePart1()
+	{
+		foreach (var (target, nums) in _data)
+		{
+			if (IsSolvable(target, nums, [Operator.Mul, Operator.Add]))
+				Part1 += target;
+		}
+	}
+
+	private bool IsSolvable(ulong target, ulong[] nums, Operator[] ops)
+	{
+		return ops.Any(o => IsSolvable(target, nums, o, nums[0], ops));
+	}
+
+	private bool IsSolvable(ulong target, ulong[] nums, Operator curOperator, ulong curTotal, Operator[] ops, int idx = 1)
+	{
+		if (target == curTotal)
+			return true;
+		if (idx >= nums.Length)
+			return false;
+
+		curTotal = curOperator switch
+		{
+			Operator.Mul => curTotal * nums[idx++],
+			Operator.Add => curTotal + nums[idx++],
+			Operator.Concat => ulong.Parse($"{curTotal}{nums[idx++]}"),
+			_ => curTotal,
+		};
+
+		return ops.Any(o => IsSolvable(target, nums, o, curTotal, ops, idx));
+	}
+
+	public override void CalculatePart2()
+	{
+		foreach (var (target, nums) in _data)
+		{
+			if (IsSolvable(target, nums, [Operator.Mul, Operator.Add, Operator.Concat]))
+				Part2 += target;
+		}
+	}
+
+	public override void LoadInput()
+	{
+		var lines = ReadInputLines("input.txt");
+		_data = new List<(ulong total, ulong[] nums)>(lines.Length);
+		foreach (var line in lines)
+		{
+			var s = line.Split(':');
+			var sum = ulong.Parse(s[0].Trim());
+			var nums = s[1].Trim().Split(' ').Select(ulong.Parse).ToArray();
+			_data.Add((sum, nums));
+		}
+	}
+}

AdventOfCode/Problems/AOC2024/Day8/ResonantCollinearity.cs

@@ -0,0 +1,139 @@
+using AdventOfCode.Utils.Models;
+
+using System.Collections.Frozen;
+
+namespace AdventOfCode.Problems.AOC2024.Day8;
+
+[ProblemInfo(2024, 8, "Resonant Collinearity")]
+internal class ResonantCollinearity : Problem<int, int>
+{
+	private string[] _map = [];
+	private int _width;
+	private int _height;
+	private FrozenDictionary<char, List<Vec2<int>>> _nodes = FrozenDictionary<char, List<Vec2<int>>>.Empty;
+
+	public override void CalculatePart1()
+	{
+		var antiNodes = new List<Vec2<int>>();
+		foreach (var (nodeType, nodes) in _nodes)
+		{
+			foreach (var a in nodes)
+			{
+				foreach (var b in nodes)
+				{
+					if (a == b)
+						continue;
+					antiNodes.AddRange(GetAntiNodes(a, b));
+				}
+			}
+		}
+		//PrintBoard(antiNodes);
+		Part1 = antiNodes.Where(IsInBounds).Distinct().Count();
+	}
+
+	public void PrintBoard(List<Vec2<int>> antinodes)
+	{
+		Console.WriteLine();
+		for (int y = 0; y < _height; y++)
+		{
+			for (int x = 0; x < _width; x++)
+			{
+				Console.ResetColor();
+				var p = new Vec2<int>(x, y);
+				if (antinodes.Contains(p))
+					Console.BackgroundColor = ConsoleColor.DarkGreen;
+				Console.Write(_map[y][x]);
+			}
+			Console.ResetColor();
+			Console.WriteLine();
+		}
+		Console.ResetColor();
+	}
+
+	public bool IsInBounds(Vec2<int> pos)
+	{
+		if (pos.X < 0 || pos.Y < 0)
+			return false;
+		if (pos.X >= _width || pos.Y >= _height)
+			return false;
+		return true;
+	}
+
+	private Vec2<int>[] GetAntiNodes(Vec2<int> a, Vec2<int> b)
+	{
+		var dir = a - b;
+
+		var aNode1 = dir + a;
+		var aNode2 = -dir + b;
+
+		return [aNode1, aNode2];
+	}
+
+	private Vec2<int>[] GetHarmonicAntiNodes(Vec2<int> a, Vec2<int> b)
+	{
+		var dir = a - b;
+
+		List<Vec2<int>> GetNodes(Vec2<int> start, Vec2<int> dir)
+		{
+			var results = new List<Vec2<int>>();
+			while (true)
+			{
+				var p = dir + start;
+				if(!IsInBounds(p))
+					break;
+				results.Add(p);
+				start = p;
+
+			}
+			return results;
+		}
+
+		return [.. GetNodes(a, dir), .. GetNodes(b, -dir)];
+	}
+
+	public override void CalculatePart2()
+	{
+		var antiNodes = new List<Vec2<int>>();
+		foreach (var (nodeType, nodes) in _nodes)
+		{
+			foreach (var a in nodes)
+			{
+				foreach (var b in nodes)
+				{
+					if (a == b)
+						continue;
+					antiNodes.AddRange(GetHarmonicAntiNodes(a, b));
+				}
+			}
+		}
+		//PrintBoard(antiNodes);
+		antiNodes.AddRange(_nodes.Values.Where(v => v.Count > 1).SelectMany(v => v));
+		Part2 = antiNodes.Distinct().Count();
+	}
+
+	public override void LoadInput()
+	{
+		_map = ReadInputLines("input.txt");
+		var nodes = new Dictionary<char, List<Vec2<int>>>();
+		_width = _map[0].Length;
+		_height = _map.Length;
+		for (int y = 0; y < _map.Length; y++)
+		{
+			var row = _map[y];
+			for (int x = 0; x < row.Length; x++)
+			{
+				switch (row[x])
+				{
+					case '.':
+						continue;
+					default:
+						var p = new Vec2<int>(x, y);
+						if (!nodes.TryAdd(row[x], [p]))
+							nodes[row[x]].Add(p);
+						continue;
+				}
+			}
+		}
+		_nodes = nodes.ToFrozenDictionary();
+	}
+}

AdventOfCode/Utils/Models/Common.cs

@@ -2,19 +2,37 @@
 
 namespace AdventOfCode.Utils.Models;
 
-
 public record struct Vec2<T>(T X, T Y) where T : INumber<T>
 {
 	public static Vec2<T> operator +(Vec2<T> left, Vec2<T> right) => new Vec2<T>(left.X + right.X, left.Y + right.Y);
 	public static Vec2<T> operator -(Vec2<T> left, Vec2<T> right) => new Vec2<T>(left.X - right.X, left.Y - right.Y);
+	public static Vec2<T> operator -(Vec2<T> vec) => new Vec2<T>(-vec.X, -vec.Y);
 	public static Vec2<T> operator *(Vec2<T> left, T right) => new Vec2<T>(left.X * right, left.Y * right);
+	public static Vec2<T> operator *(T left, Vec2<T> right) => new Vec2<T>(right.X * left, right.Y * left);
 	public static Vec2<T> operator /(Vec2<T> left, T right) => new Vec2<T>(left.X / right, left.Y / right);
+
+	public T DistanceSq(Vec2<T> other)
+	{
+		var a = other.X - this.X;
+		var b = other.Y - this.Y;
+		return (a * a) + (b * b);
+	}
 }
 
 public record struct Vec3<T>(T X, T Y, T Z) where T : INumber<T>
 {
 	public static Vec3<T> operator +(Vec3<T> left, Vec3<T> right) => new Vec3<T>(left.X + right.X, left.Y + right.Y, left.Z + right.Z);
 	public static Vec3<T> operator -(Vec3<T> left, Vec3<T> right) => new Vec3<T>(left.X - right.X, left.Y - right.Y, left.Z - right.Z);
+	public static Vec3<T> operator -(Vec3<T> vec) => new Vec3<T>(-vec.X, -vec.Y, -vec.Z);
 	public static Vec3<T> operator *(Vec3<T> left, T right) => new Vec3<T>(left.X * right, left.Y * right, left.Z * right);
+	public static Vec3<T> operator *(T left, Vec3<T> right) => new Vec3<T>(right.X * left, right.Y * left, right.Z * left);
 	public static Vec3<T> operator /(Vec3<T> left, T right) => new Vec3<T>(left.X / right, left.Y / right, left.Z / right);
+
+	public T DistanceSq(Vec3<T> other)
+	{
+		var a = other.X - this.X;
+		var b = other.Y - this.Y;
+		var c = other.Z - this.Z;
+		return (a * a) + (b * b) + (c * c);
+	}
 }