AdventOfCode/2022/Day07CSharp/Program.cs

// See https://aka.ms/new-console-template for more information
using System.ComponentModel;
using System.Drawing;
using System.Xml;

Console.WriteLine("Hello, World!");

Directory exampleRoot = LoadData("example-input.txt");
Directory puzzleRoot = LoadData("puzzle-input.txt");

Console.WriteLine(String.Format("Part01: Example({0}), Puzzle({1})", Part01(exampleRoot, 100000), Part01(puzzleRoot, 100000)));

Console.WriteLine(String.Format("Part02: Example({0}), Puzzle({1})" , Part02(exampleRoot, 70000000 - exampleRoot.Size, 30000000, exampleRoot.Size)
                                                                    , Part02(puzzleRoot, 70000000 - puzzleRoot.Size, 30000000, puzzleRoot.Size)));

int Part01(Directory root, int maxsize)
{
    int returnSize = 0;
    int size = 0;

    foreach (var file in root.Files)
    {
        size += file.Size;
    }
    foreach (var subdir in root.SubDirectories)
    {
        size += subdir.Size; 
    }

    if (size < maxsize) returnSize += size;

    foreach (var subdir in root.SubDirectories)
    {
        returnSize += Part01(subdir, maxsize);
    }

    return returnSize;
}

int Part02(Directory root, int unusedSpace, int targetUnusedSpace, int returnSize)
{
    if (unusedSpace + root.Size > targetUnusedSpace)
    {
        returnSize = Int32.Min(returnSize, root.Size);
    }
    

    foreach (var subdir in root.SubDirectories)
    {
        returnSize = Int32.Min(returnSize, Part02(subdir, unusedSpace, targetUnusedSpace, returnSize));
    }

    return returnSize;
}

Directory LoadData(string fileName)
{
    Directory root = new Directory("/", null);
    Directory currentDir = root;

    using (StreamReader reader = System.IO.File.OpenText(fileName))
    {
        while (!reader.EndOfStream)
        {
            string? line = reader.ReadLine();
            if (line == null) throw new InvalidDataException();
            if (line.Length == 0) continue;

            // We should be reading commands here
            if (line.StartsWith('$'))
            {
                var split = line.Split(' ');

                if (split[1].StartsWith("cd"))
                {
                    if (split.Length != 3)
                    {
                        throw new InvalidDataException();
                    }
                    currentDir = HandleChangeDirectory(reader, split[2], currentDir);
                } 
                else if (split[1].StartsWith("ls"))
                {
                    currentDir = HandleListDirectory(reader, currentDir);
                }
            }
            else
            {
                throw new InvalidDataException();
            }
        }

    }

    return root;
}

Directory HandleListDirectory(StreamReader reader, Directory currentDir)
{
    while (!reader.EndOfStream && reader.Peek() != '$')
    {
        string? line = reader.ReadLine();
        if (line == null) throw new InvalidDataException();

        var split = line.Split(" ");

        int size = 0;

        if (split[0].StartsWith("dir"))
        {
            if (currentDir.SubDirectories.Exists(x => x.Name.StartsWith(split[1])))
            {
                throw new InvalidDataException();
            }
            currentDir.SubDirectories.Add(new Directory(split[1], currentDir));
        }
        else if (Int32.TryParse(split[0], out size))
        {
            if (currentDir.Files.Exists(x => x.Name == split[1]))
            {
                throw new InvalidDataException();
            }
            currentDir.Files.Add(new File(split[1], size));
        }
        else
        { throw new InvalidDataException(); }
    }

    return currentDir;
}

Directory HandleChangeDirectory(StreamReader reader, string argument, Directory currentDir)
{
    switch (argument)
    {
        case "/":
            while (currentDir != null && !currentDir.Name.StartsWith("/")) 
            {
                if (currentDir.Parent == null) throw new InvalidDataException();
                currentDir = currentDir.Parent;
            }
            return currentDir;

        case "..":
            if (currentDir.Parent == null)
            {
                throw new InvalidDataException();
            }

            currentDir = currentDir.Parent;
            return currentDir;

        default:
            foreach (var subdir in currentDir.SubDirectories)
            {
                if (subdir.Name == argument)
                {
                    currentDir = subdir;
                    return currentDir;
                }
            }
            throw new InvalidDataException();
    }
}

class File
{
    public string Name { get; set; }
    public int Size { get; set; }

    public File(string name, int size)
    {
        Name = name;
        Size = size;
    }
}
class Directory
{
    public List<Directory> SubDirectories { get; set; } = new List<Directory>();
    public List<File> Files { get; set; } = new List<File>();
    public Directory? Parent { get; set; } = null;

    public string Name { get; set; }

    public Directory(string name, Directory parent) { Name = name; Parent = parent; }

    public int Size
    {
        get
        {
            int size = 0;

            foreach (var subdir in SubDirectories)
            {
                size += subdir.Size;
            }
            foreach (var file in Files)
            {
                size += file.Size;
            }

            return size;
        }
    }
}