20221201-advent-of-code-part1.cs

var lines = File.ReadAllLines("day1.txt");

var state = lines.Aggregate(new State(new ElfCalories(0, 0), new ElfCalories(0, 0)), (state, line) =>
{

    if (line == string.Empty)
    {
        return NextState(state);
    }
    var calories = int.Parse(line);
    var current = state.Current with { Calories = state.Current.Calories + calories };

    state = new State(current, GetMaxElf(current, state.Max));
    return state;
});

Console.WriteLine($"Elf: {state.Max.Elf + 1} with {state.Max.Calories} calories");

State NextState(State state) =>
    new State(
        new ElfCalories(state.Current.Elf + 1, 0),
        GetMaxElf(state.Current, state.Max)
    );

ElfCalories GetMaxElf(ElfCalories elf1, ElfCalories elf2) => elf1.Calories > elf2.Calories ? elf1 : elf2;

record ElfCalories(int Elf, int Calories);

record State(ElfCalories Current, ElfCalories Max);

20221201-advent-of-code-part2.cs

using System.Collections.Immutable;

var lines = File.ReadAllLines("day1.txt");

var state = lines.Aggregate(new State(new ElfCalories(0, 0), ImmutableArray<ElfCalories>.Empty), (state, line) =>
{

    if (line == string.Empty)
    {
        return NextState(state);
    }
    var calories = int.Parse(line);
    state.Current.Calories += calories;
    return state with { Max = GetMaxElves(state.Max.Add(state.Current)) };
});

foreach (var elfCalories in state.Max)
{
    Console.WriteLine($"Elf {elfCalories.Elf + 1} with {elfCalories.Calories} calories");
}


Console.WriteLine($"{state.Max.Sum(elf => elf.Calories)} total calories");

State NextState(State state)
{

    return new State(
        new ElfCalories(state.Current.Elf + 1, 0),
        GetMaxElves(state.Max.Add(state.Current))
    );
}

ImmutableArray<ElfCalories> GetMaxElves(ImmutableArray<ElfCalories> elves)
{
    return elves.DistinctBy(elf => elf.Elf).OrderByDescending(elf => elf.Calories).Take(3).ToImmutableArray();
};

class ElfCalories
{
    public ElfCalories(int Elf, int Calories)
    {
        this.Elf = Elf;
        this.Calories = Calories;
    }

    public int Elf { get; }
    public int Calories { get; set; }
}

record State(ElfCalories Current, ImmutableArray<ElfCalories> Max);

20221202-advent-of-code-part1.cs

var lines = File.ReadAllLines("day1.txt");
var total = 0;
foreach (var line in lines)
{
    var parts = line.Split(' ');
    var opp = GetHand(parts[0][0]);
    var player = GetHand(parts[1][0]);
    var score = GetScore(opp, player);
    total += score;
}

Console.WriteLine(total);


Hand GetHand(char c) => (Hand)(c is >= 'A' and <= 'C' ? c - 'A' : c - 'X');

State GetOutcome(Hand opponent, Hand player)
{
    if (opponent == player) return State.Draw;

    return opponent switch
    {
        Hand.Rock => player == Hand.Paper ? State.Win : State.Loss,
        Hand.Paper => player == Hand.Scissors ? State.Win : State.Loss,
        Hand.Scissors => player == Hand.Rock ? State.Win : State.Loss,
        _ => throw new ArgumentOutOfRangeException(nameof(opponent), opponent, null)
    };
}

int GetScore(Hand opp, Hand player)
{
    var shapeSelection = (int)player + 1;
    var outcome = GetOutcome(opp, player);
    return shapeSelection + (int)outcome;
}

enum State
{
    Loss = 0,
    Draw = 3,
    Win = 6,
}

enum Hand
{
    Rock = 0, Paper = 1, Scissors = 2,
}

20221202-advent-of-code-part2.cs

var lines = File.ReadAllLines("day1.txt");
var total = 0;
foreach (var line in lines)
{
    var parts = line.Split(' ');
    var opp = GetHand(parts[0][0]);
    var outcome = GetOutcomeFromString(parts[1][0]);
    var player = GetPlayerHand(opp, outcome);
    var score = GetScore(opp, player);
    total += score;
}

Console.WriteLine(total);


Hand GetHand(char c) => (Hand)(c is >= 'A' and <= 'C' ? c - 'A' : c - 'X');

Hand GetPlayerHand(Hand opponent, Outcome outcome)
{
    if (outcome == Outcome.Draw) return opponent;

    return opponent switch
    {
        Hand.Rock => outcome == Outcome.Win ? Hand.Paper : Hand.Scissors,
        Hand.Paper => outcome == Outcome.Win ? Hand.Scissors : Hand.Rock,
        Hand.Scissors => outcome == Outcome.Win ? Hand.Rock : Hand.Paper,
        _ => throw new ArgumentOutOfRangeException(nameof(opponent), opponent, null)
    };
}

Outcome GetOutcomeFromString(char c) => (Outcome )(c - 'X');

Outcome GetOutcome(Hand opponent, Hand player)
{
    if (opponent == player) return Outcome.Draw;

    return opponent switch
    {
        Hand.Rock => player == Hand.Paper ? Outcome.Win : Outcome.Loss,
        Hand.Paper => player == Hand.Scissors ? Outcome.Win : Outcome.Loss,
        Hand.Scissors => player == Hand.Rock ? Outcome.Win : Outcome.Loss,
        _ => throw new ArgumentOutOfRangeException(nameof(opponent), opponent, null)
    };
}

int GetScore(Hand opp, Hand player)
{
    var shapeSelection = (int)player + 1;
    var outcome = GetOutcome(opp, player);
    return shapeSelection + GetOutcomeScore(outcome);
}

int GetOutcomeScore(Outcome outcome) =>
    outcome switch
    {
        Outcome.Loss => 0,
        Outcome.Draw => 3,
        Outcome.Win => 6,
        _ => throw new ArgumentOutOfRangeException(nameof(outcome), outcome, null)
    };

enum Outcome
{
    Loss = 0,
    Draw = 1,
    Win = 2,
}

enum Hand
{
    Rock = 0, Paper = 1, Scissors = 2,
}

20221203-advent-of-code-part2.cs

// See https://aka.ms/new-console-template for more information

var lines = File.ReadAllLines("day3.txt");
var total = 0;
for (int i = 0; i < lines.Length; i+=3)
{
    total += GetPriority(GetBadge(lines, i));
}

Console.WriteLine(total);

char GetBadge(string[] strings, int index)
{
    var set1 = new HashSet<char>();
    foreach (var c in strings[index])
    {
        set1.Add(c);
    }

    var set2 = new HashSet<char>();
    foreach (var c in strings[index + 1])
    {
        if (set1.Contains(c))
            set2.Add(c);
    }

    foreach (var c in strings[index + 2])
    {
        if (set2.Contains(c))
        {
            Console.WriteLine(c);
            return c;
        }
    }

    throw new InvalidOperationException();
}

int GetPriority(char c) =>
    c switch
    {
        >= 'a' and <= 'z' => c - 'a' + 1,
        >= 'A' and <= 'Z' => c - 'A' + 27,
        _ => throw new InvalidOperationException()
    };

20221204-advent-of-code-part2.cs

var lines = File.ReadAllLines("day1.txt");
var total = 0;
foreach (var line in lines)
{
    var elves = line.Split(',');
    var elf1 = Span.Parse(elves[0]);
    var elf2 = Span.Parse(elves[1]);

    if (elf1.Overlaps(elf2))
        total++;

}

Console.WriteLine(total);


record Span(int Start, int End)
{
    public bool Overlaps(Span span) =>
        Contains(span.Start) || Contains(span.End) ||
        span.Contains(Start) || span.Contains(End);
    public bool Contains(int position) => position >= Start && position <= End;
    public bool Contains(Span span) => Contains(span.Start) && Contains(span.End);

    public static Span Parse(string value)
    {
        var parts = value.Split('-');
        return new Span(int.Parse(parts[0]), int.Parse(parts[1]));
    }
}

20221205-advent-of-code-part1.cs

using System.Collections.Immutable;

var lines = File.ReadAllLines("day1.txt");
var total = 0;
var puzzle = Puzzle.Parse(lines.TakeWhile(line => line.Trim() != "").ToArray());

var moveLines = lines.SkipWhile(line => line.Trim() != "").Skip(1).ToArray();
foreach (var line in moveLines)
{
    // move 1 from 2 to 1
    var command = line.Split(' ');
    var quantity = int.Parse(command[1]);
    var from = int.Parse(command[3]);
    var to = int.Parse(command[5]);
    puzzle.Move(from, to, quantity);
}

Console.WriteLine(puzzle.Tops);


record Puzzle(Dictionary<int, Stack<char>> Stacks)
{

    public string Tops => string.Join("", Stacks.OrderBy(kv => kv.Key).Select(kv => kv.Value.Peek()));

    public void Move(int from, int to, int quantity)
    {
        while (quantity-- > 0)
        {
            Move(from, to);
        }
    }

    public void Move(int from, int to) => Stacks[to].Push(Stacks[from].Pop());

    public static Puzzle Parse(string[] lines)
    {
        var ids = lines[^1]
            .Split(' ', StringSplitOptions.RemoveEmptyEntries)
            .Select(id => int.Parse(id.Trim()))
            .ToArray();

        var stacks = ids.ToDictionary(id => id, _ => new Stack<char>());

        for (var i = lines.Length - 2; i >= 0; i--)
        {
            // first char index is 1
            // next is 5
            var line = lines[i];
            foreach (var id in ids)
            {
                var index = 1 + 4 * (id - 1);
                if (index < line.Length && line[index] != ' ')
                    stacks[id].Push(line[index]);
            }
        }

        return new Puzzle(stacks);
    }
}

20221205-advent-of-code-part2.cs

using System.Collections.Immutable;

var lines = File.ReadAllLines("day1.txt");
var total = 0;
var puzzle = Puzzle.Parse(lines.TakeWhile(line => line.Trim() != "").ToArray());

var moveLines = lines.SkipWhile(line => line.Trim() != "").Skip(1).ToArray();
foreach (var line in moveLines)
{
    // move 1 from 2 to 1
    var command = line.Split(' ');
    var quantity = int.Parse(command[1]);
    var from = int.Parse(command[3]);
    var to = int.Parse(command[5]);
    puzzle.Move(from, to, quantity);
}

Console.WriteLine(puzzle.Tops);


record Puzzle(Dictionary<int, Stack<char>> Stacks)
{

    public string Tops => string.Join("", Stacks.OrderBy(kv => kv.Key).Select(kv => kv.Value.Peek()));

    public void Move(int from, int to, int quantity)
    {
        var stack = new Stack<char>();
        var a = quantity;
        while (a-- > 0)
        {
            stack.Push(Stacks[from].Pop());
        }

        a = quantity;
        while (a-- > 0)
        {
            Stacks[to].Push(stack.Pop());
        }
    }

    public static Puzzle Parse(string[] lines)
    {
        var ids = lines[^1]
            .Split(' ', StringSplitOptions.RemoveEmptyEntries)
            .Select(id => int.Parse(id.Trim()))
            .ToArray();

        var stacks = ids.ToDictionary(id => id, _ => new Stack<char>());

        for (var i = lines.Length - 2; i >= 0; i--)
        {
            // first char index is 1
            // next is 5
            var line = lines[i];
            foreach (var id in ids)
            {
                var index = 1 + 4 * (id - 1);
                if (index < line.Length && line[index] != ' ')
                    stacks[id].Push(line[index]);
            }
        }

        return new Puzzle(stacks);
    }
}

20221206-advent-of-code-part2.cs

var input = "hlfhfzffqnnrlnnvnmmgbgwgttbppcrcnnmdmfdmmgwwrrqnrrscrctcbttvcvtvvhchjhccjgjttmddplplqplqlbqlblrrbrvvprpffpmmzpmpcczjzzbwwfssvrrvggncgncgcwczzswwqqjjflffpwfpwpbwpwpdpbpvvqffcfcjffjllncczfzzmhzzmddgdrgrwwjzzdjjsnjsjfsjsjhhcchlccchqchhzzpnngdgndnpnppsdsggbvgvgpprqrqmmlzmzllvrrcvclcwczcqqcdcfcqqmmzbzdzdjzdjdmjdjzdjjcvjvcjvcvssltstttfbtftrfrlrdllrqqfssslccjdcjdjfdjfjqjnqjnjnrnddtnndtnnztzqztqztqzzpmzmggzrgrwwdqwdwcdwdnnmlmgmtmtstwssbffcnclclnclcjjcjpcpqcpqcpqpmqqfccpcjppnspsnnzggnpntndtdqtthwhnhwnwllzhlzhlzzghzghhlhvhwhjhfjjcnjnvjnjvvqccdmmgddllnmnrrdtdnncggfhgfglfgfmfnnpvvggznnwvnwwfgghrrfwrwzwszzzldzdldhlhblhblhbbbgjgsjggmqqmrrzggrhhwpwdpwdpwplpgpbggtssqffbqfbqbnnsqnqfnngcnnmwnmnbmmmslsjllbtbbpllltzzhgzztllsdllrvvhvjvbbhcbhchmchcctbcttvccgwcwpcchrcrdrdggcrrntrrfllcffbdfflrrrgbgrbbbdqbqjbbgbgrrqwqtwqwhwghwhzwwcswsnwnqqjhjhwhfwhffdfgddgjgsjgjhgglhlwhlhssfqfhhdmdnmnppdcddfzzhmhqqntqnnjvnjvjddcvcgcbgbbpjbjtbjjfgftgffplljfjrrhqqpddlssrvsrvrpppsllsdsqqqzzfttqsqzssjbbrnbnnrbbsrshsrrshrhwhbwbrrsrfrttfqtfqqfddvrvjrjvjsjhjsjdjqdjjlqjjjgcjcmcncfcrcwrwsrsslffzszmsszrsssrnrjjvbvpvcppptbbhhrddbcbggbqbmmsqqwggfpfbblmldmmpmwpwfwjfjsjnjmmpllccjzcjcwwpswshhpthhzchctcbcrrrrmvrvrdvvjmmvgmgwglghllvmllzlzzsvzzrmmhnnsjnnpvpwvpwwmvwwdqqdffhhhmccfgfvggchcctrrmdrrhrhnhnzzgpzzgttnhthvhzzqvvvwpwqpqdppsnnrgnnhphphmhcmcrmrvvqlvqqsccqhchzhwwmvmzmczzgsgdsggthgglrlnrlllbdllhwlwltwwcswsgssbhbsbvsbsbwbhbnncrcllttbrbppjccfpfhhgshschsccmrcmmcrrrzvvrcrggmwgwjwnwjjbffjddjnjgngqgdgnndznndvvfqfgfvvrvqrvvpllnsszbsbdbbdzbdbzbqbzznrznzjzpptcptccvwccfscffrftrrsnsvvswvvhbhzzfbzffncchhcnngzzcpcmmfttsntnjjsccqbcqqmzzgppdhppdtppmffgtgvvlzlpptdtttdppqjqtqctcrrzsswwtnwtnwnqqvbbdgjhvmmzpnhfvsbddzhgdwcnfdstvhhbzlzcfjwhlptbhmbmblprtsdmrdhbbbwpplnzgdnrzjmgzgpqbggnqvwwtntzgfwqrztqtdrsnhpfzswptggnvbszdcrmrhhtlrrfnpqrnpwrbmhlfwmdqqdbqrwbzqjbzwrgmbgrtzrhdclqfgsrtsgfwqrnnqgwsncmpgffggssrqvwjlhpsghbqdtzwmvzzvcmzsjqvprvcqwqjbcqcqrhpwwcsrscgmfdppbgvmnrdfrppblznbstnjzwwgstjvtprjbhtpdfgrhdjnjmnlbfwggzhcngvcwvcfpcwdtdppwjrdzsnjlnrzbfqqshlnzvwsmscgpfwjzhtwgfwgzdhbdwwzbsmfwwbmvrlrpswnjlmfbfzhwvcmgwfzssmmtjlwtrpwpwgnspbgchdncbfcpjsvtzjqtwqwjwgbhrbwvhqbcstsgsnwsjmhrlrvzgqhqfrmnrjdrhdjwcwctpdrzctlvnfzmzwhsnfprlzgzjpqvzchlmvbhffhpfjtvsdbvbdmwgvmqpflhwwndbqthmmwshdtspsrvqdflmmzwbqbqmpfdwjmvpbzdnqzfmhzdgldqjjvgpfcqftvjzwnzmfqdggrwlfzdhjnhmtrjbnllgqpntwmhnwtglnqdwbqdblpwnnrdwzpsqzfwqcmhqhnpsdcwvdldphgnrtqzdbnnzdzfttldrqcztlvlrgpdqzrcthslmtqhfvbzrfgnlrprcpbsctqhspbhnjtzrzhqjzszbzdthttqmbznzssftztwlggmdqqdtfllqjzjtvpgjfhtbwtbmtjplqnbdmsvlnqcwtdbdvfjnzgsmpnhbvvwwfbrgffjqfsccdjdwvbsdhqwfzvcpjzjbdjgrdctjplhwbdhhnbnwstvndnnwtsgbhzbvwdshvmnbwsthlrggtmddvjbfzfrnrdrqfjpslrccctzpjbwpdbhlbzfmwbltcqfngdprvfhgcszdtpnrcpdmllfnlspgrdrpwqmqbmrglvlrsmrfqrtzzgjcvqtqzpmghjrvmdmvvqztrjzbzjwdqsmrwpqnswbzhjbzzhdvmnfdsztzdzrjssgnnfqvbtsqrrmcppjgrmnstrnrlwjvvcczqlcbmwqzdfpssfwdfrvwtstwchdgwtrhhcmppcqlmrqlnwqccfphsdhbsbmtjvpcwwjrmrllbpnrmpbvwgwbftpdpphccwqcblcnvvbbppscmnjqgddllbnbvmmqzdffrrjtqwllzgpqrmnlfqrptzqmdmnrfnjpvqvjbsqrhljslgqqcqqtmtbwjrpphtjgjbqpzmzrzjrfjwcdcnbsjfljclffjplnrrcfbmhphtcjrzlrvvjcznpgpnrdwwqvgnbnzqnlcghhgwvhqbvjzfbdvhrzlqfbtlqhpltfjlfpbnjbphmmpntzqgjmwjtchwmlwvfjmfflqzpqnvvrgnbddzlfpdpdjghfgbsfddjspnfdwvqppncmdgfrnvrpcrflhgjgbwdsbwblfcwbtlrrnjjdhbvmrzgsvjwgfnnhqfbvhprlmwwqgclzlbqbrdspcbhftmdscsmpwrggrmnsvjphjmzmmrlrhnmdhwjlbmjchtvsrcplfspsssjznmzcrqnsjjtwjzvlhshbptqwwvjhjvzrhphphsbphpnzpfbwcdnqrhrrvlrwrztlpqnrcfzrncsvpzqzgslrlrwhvtgjmfncldqmvshlmnlpqbgvnwqfcthgrgllmqrjqmfgznspgltpptglpdcvhtzsprprbldbzhbmjsqzwvjggwhsczltcvgwqhspzpzvljwqjgrgtwswjdswlzjzslrsslvqzncjwhbbjpbdthqpgmhfglggmlrgwdsplgscrwstntvrhjzjjlshtgmnnhvsjwfmcjbpzjcstmnpvtbgrfcfdwjljsrfhdphrdcslwhgvlnwltwchplvfzntfgcnlsvzrvnnczhhqdlwjvqprhmtjdtwmppffmszzzqtfrgnhnzqgqzhrjzgntcszstrfhhtptgvswvzvjcgcntmhzzmdgsmtgzhpfvqfnwmsjdhtfgmmbrrfsdlptchqqzqdqjncmtpznfssrcnmcdnthglmfzsfgltrndqsfmdftmfgchbwmzgrtjvgqtshlltthnnpqnzfrchzhdzrrnpzvfzblrmhwdwjnqdptlbvndmmlhzhvsfdlmlhqrgqqzsdqtpczwcrwcbsftvvphfbwjrvrnrcqbbcsqgnhltwzvllljcvpwjgslbmngcdmpdvjlgcnrzwqjdgrblncpqmrgjmpqjzvdmcmwfnwqlszdgwqdfznhsnpsjrfwrqpqmpvhstmzgqblfmcfvwljbhdfhdmqcvrwnqcstwtzgmng";


Console.WriteLine(DetectMarker(input, 14));

int DetectMarker(string signal, int size)
{
    var marker = signal.Take(size).ToArray();
    var index = size - 1;
    while (marker.Distinct().Count() < size)
    {
        index++;
        marker[index % size] = signal[index];
    }

    return index + 1;
}

20221208-advent-of-code-part1.cs

// build map
var input = File.ReadAllLines("day1.txt");
var width = input[0].Length;
var height = input.Length;
var map = new int[width, height];
var visible = new int[width, height];
for (var y = 0; y < height; y++)
for (var x = 0; x < width; x++)
{
    map[x, y] = input[x][y] - '0';
}

var count = 0;
for (var y = 0; y < height; y++)
for (var x = 0; x < width; x++)
{
    if (IsVisible(x, y))
    {
        visible[x, y] = 1;
        count++;
    }
}

Console.WriteLine(count);

bool IsVisible(int x, int y)
{
    if (x == 0 || y == 0) return true;
    if (x == width - 1 || y == height - 1) return true;

    var currHeight = map[x, y];
    // from left
    if (IsVisibleFrom(x, y, -1, 0, currHeight)) return true;
    // from right
    if (IsVisibleFrom(x, y, 1, 0, currHeight)) return true;
    // from top
    if (IsVisibleFrom(x, y, 0, -1, currHeight)) return true;
    // from bottom
    if (IsVisibleFrom(x, y, 0, 1, currHeight)) return true;

    return false;
}

bool IsVisibleFrom(int x, int y, int dx, int dy, int maxHeight)
{
    // out of bounds
    if (x + dx < 0 || x + dx >= width) return true;
    if (y + dy < 0 || y + dy >= height) return true;

    var currHeight = map[x + dx, y + dy];
    if (currHeight >= maxHeight) return false;

    return IsVisibleFrom(x + dx, y + dy, dx, dy, maxHeight);
}

20221208-advent-of-code-part2.cs

// build map
var input = File.ReadAllLines("day1.txt");
var width = input[0].Length;
var height = input.Length;
var map = new int[width, height];
for (var y = 0; y < height; y++)
for (var x = 0; x < width; x++)
{
    map[x, y] = input[x][y] - '0';
}

var maxScore = -1;

for (var y = 0; y < height; y++)
for (var x = 0; x < width; x++)
{
    maxScore = Math.Max(maxScore, GetScenicScore(x, y));
}

Console.WriteLine(maxScore);


int GetScenicScore(int x, int y)
{
    var h = map[x, y];
    var left = GetViewingDistance(x, y, -1, 0, h);
    var right = GetViewingDistance(x, y, 1, 0, h);
    var up = GetViewingDistance(x, y, 0, -1, h);
    var down = GetViewingDistance(x, y, 0, 1, h);

    return left * right * up * down;
}

int GetViewingDistance(int x, int y, int dx, int dy, int maxHeight, int trees = 0)
{
    // out of bounds
    if (x + dx < 0 || x + dx >= width) return trees;
    if (y + dy < 0 || y + dy >= height) return trees;

    var currHeight = map[x + dx, y + dy];

    // tree blocks
    if (currHeight >= maxHeight) return trees + 1;

    return GetViewingDistance(x + dx, y + dy, dx, dy, maxHeight, trees + 1);
}