#define Day14
#if Day14
using System.Text.RegularExpressions;
using AoC2021;
var text = File.ReadAllText("day14/input").Split("\n\n");
var startOne = text[0].Select(x => x).ToList();
var startTwo = startOne.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 < startOne.Count; pos++) {
//         var res = rules[new Pair(startOne[pos - 1], startOne[pos])];
//         next.Add(startOne[pos - 1]);
//         next.Add(res);
//     }
//     next.Add(startOne.Last());
//     startOne = next;
// }
//
// var charCountPartOne = startOne.GroupBy(s => s).ToDictionary(g => g.Key, g => g.LongCount());
// Console.WriteLine(charCountPartOne.Values.Max() - charCountPartOne.Values.Min());
//
// var charCountPartTwo = rules.Keys.SelectMany(r => new List<char>(){r.a, r.b}).Distinct().ToDictionary(x => x, _ => 0L);
int maxDepth = 40;

var finalCount = new Dictionary<char, long>();
var save = new Dictionary<AsKey, Dictionary<char, long>>();

Dictionary<char, long> Bla(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 = Bla(new Pair(cur.a, c), depth - 1);
    var second = Bla(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) {
    var merged = new Dictionary<char, long>();
    foreach (var k in a.Keys) {
        merged.Add(k, a[k]);
    }
    foreach (var k in b.Keys) {
        if (merged.ContainsKey(k)) {
            merged[k] += b[k];
        } else {
            merged[k] = b[k];
        }
    }

    return merged;
}

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

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

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