day 12 part 1

AdventOfCode/Problems/AOC2024/Day12/GardenGroups.cs

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+using AdventOfCode.Utils.Models;
+
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace AdventOfCode.Problems.AOC2024.Day12;
+
+[ProblemInfo(2024, 12, "Garden Groups")]
+internal class GardenGroups : Problem<int, int>
+{
+	private char[][] _data = [];
+
+	public readonly static Vec2<int>[] DIRS = [
+			new(0,1),
+			new(1,0),
+			new(0,-1),
+			new(-1,0),
+		];
+
+	public override void CalculatePart1()
+	{
+		var r = FindPlots(_data);
+		Part1 = r.Sum(plot => plot.area.Count * plot.perimeter);
+	}
+
+	public override void CalculatePart2()
+	{
+		var r = FindPlots(_data).Select(plot => (plot.plant, plot.area.Count, CountSides(plot.outline)));
+	}
+
+	private static int CountSides(List<Vec2<int>> perimeter)
+	{
+		if (perimeter.Count <= 2)
+			return 4;
+		var sides = 1;
+
+		var lastDir = new Vec2<int>(0,0);
+		//var startDir = lastDir;
+		for (int i = 0; i < perimeter.Count; i++)
+		{
+			var p = perimeter[i];
+			var p2 = perimeter[(i + 1) % perimeter.Count];
+			var dir = p - p2;
+			if(dir != lastDir)
+				sides++;
+			lastDir = dir;
+		}
+
+		return sides < 4 ? 4 : sides;
+	}
+
+	private static List<(char plant, List<Vec2<int>> area, int perimeter, List<Vec2<int>> outline)> FindPlots(char[][] data)
+	{
+		var visited = new HashSet<Vec2<int>>(data.Length * data[0].Length);
+
+		var results = new List<(char plant, List<Vec2<int>>, int perimeter, List<Vec2<int>> outline)>();
+
+		for (int y = 0; y < data.Length; y++)
+		{
+			var row = data[y];	
+			for (int x = 0; x < row.Length; x++)
+			{
+				var p = new Vec2<int>(x, y);
+				if (visited.Contains(p))
+					continue;
+				var members = new List<Vec2<int>>();
+				var plant = data[y][x];
+				var perimeter = 0;
+				var outline = new List<Vec2<int>>();
+				GetMembers(data, plant, p,visited, members, ref perimeter, outline);
+				results.Add((plant, members, perimeter, outline));
+			}
+		}
+		return results;
+	}
+
+	private static void GetMembers(char[][] data, char plant, Vec2<int> point, HashSet<Vec2<int>> visited, List<Vec2<int>> members, ref int perimeter, List<Vec2<int>> outline)
+	{
+		if (visited.Contains(point))
+			return;
+		visited.Add(point);
+		members.Add(point);
+
+		foreach (var dir in DIRS)
+		{
+			var n = dir + point;
+			if (!IsInBounds(n, data))
+			{
+				perimeter += 1;
+				outline.Add(n);
+				continue;
+			}
+			if (data[n.Y][n.X] != plant)
+			{
+				perimeter += 1;
+				outline.Add(n);
+				continue;
+			}
+			GetMembers(data, plant, n, visited, members, ref perimeter, outline);
+		}
+
+	}
+
+	public static bool IsInBounds(Vec2<int> pos, char[][] data)
+	{
+		if (pos.X < 0 || pos.Y < 0)
+			return false;
+		if (pos.X >= data.Length || pos.Y >= data[0].Length)
+			return false;
+		return true;
+	}
+
+	
+
+	public override void LoadInput()
+	{
+		_data = ReadInputLines("sample.txt").Select(ln => ln.ToCharArray()).ToArray();
+	}
+}