// #define Day14
#if Day14
using System.Text.RegularExpressions;
var text = File.ReadAllText("day14/input").Split("\n\n");
var start = text[0].Select(x => x).ToList();

var reg = new Regex(@"(?<a>\w)(?<b>\w) -> (?<res>\w)");
var rules = reg.Matches(text[1]).Select(m => new Rule(new Pair(m.Groups["a"].Value[0], m.Groups["b"].Value[0]), m.Groups["res"].Value[0])).ToDictionary(x => x.p, x=> x.res);

for (var i = 0; i < 10; i++) {
    var next = new List<char>();
    for (int pos = 1; pos < start.Count; pos++) {
        var res = rules[new Pair(start[pos - 1], start[pos])];
        next.Add(start[pos - 1]);
        next.Add(res);
    }
    next.Add(start.Last());
    start = next;
}

var charCountPartOne = start.GroupBy(s => s).ToDictionary(g => g.Key, g => g.LongCount());
Console.WriteLine(charCountPartOne.Values.Max() - charCountPartOne.Values.Min());

// Part two
start = text[0].Select(x => x).ToList();
int maxDepth = 40;
var charCountPartTwo = new Dictionary<char, long>();
var save = new Dictionary<AsKey, Dictionary<char, long>>();

Dictionary<char, long> Process(Pair cur, int depth) {
    var curKey = new AsKey(cur, depth);
    if (save.ContainsKey(curKey)) {
        return save[curKey];
    }
    if (depth <= 0) {
        return new Dictionary<char, long>() { {cur.a, 1} };
    }

    var c = rules[cur];
    var first = Process(new Pair(cur.a, c), depth - 1);
    var second = Process(new Pair(c, cur.b), depth - 1);

    var merged = Merge(first, second);
    save[curKey] = merged.ToDictionary(x => x.Key, x => x.Value);

    return merged;
}

Dictionary<char, long> Merge(Dictionary<char, long> a, Dictionary<char, long> b) {
    return new List<Dictionary<char, long>>(){a, b}.SelectMany(x => x)
        .ToLookup(pair => pair.Key, pair => pair.Value)
        .ToDictionary(group => group.Key, group => group.Sum());
}

for (int pos = 1; pos < start.Count; pos++) {
    var countBla = Process(new Pair(start[pos - 1], start[pos]), maxDepth);
    charCountPartTwo = Merge(charCountPartTwo, countBla);
}
charCountPartTwo[start.Last()]++;

Console.WriteLine(charCountPartTwo.Values.Max() - charCountPartTwo.Values.Min());

record AsKey(Pair p, int depth);
record Rule(Pair p, char res);
record Pair(char a, char b);
#endif