// #define Day15
#if Day15
using System.Collections.Immutable;
using System.Diagnostics;
using AoC2021;

var lines = File.ReadAllLines("day15/input");
var cave = new int[lines.Length, lines[0].Length];
lines.ForEachIndex((l, row) => l.ForEachIndex((c, col) => cave[row, col] = int.Parse(c.ToString())));

Console.WriteLine(Check(cave));

int rowLength = cave.GetLength(0);
int colLength = cave.GetLength(1);
var largerCave = new int[lines.Length * 5, lines[0].Length * 5];
for (int timeRow = 0; timeRow < 5; timeRow++) {
    for (int timesCol = 0; timesCol < 5; timesCol++) {
        for (int row = 0; row < rowLength; row++) {
            for (int col = 0; col < colLength; col++) {
                largerCave[rowLength * timeRow + row, colLength * timesCol + col] = ((cave[row, col] + timeRow + timesCol - 1) % 9) + 1;
            }
        }
    }
}

Console.WriteLine(Check(largerCave));

long Check(int[,] caveToCheck) {
    var pos = new Point(0, 0);
    var end = new Point(caveToCheck.GetLength(0) - 1, caveToCheck.GetLength(1) - 1);
    var visitedLowest = new Dictionary<Point, long>() { { pos, 0 } };
    var minPaths = new PriorityQueue<PointWithVisited, long>();
    minPaths.Enqueue(new PointWithVisited(pos, ImmutableHashSet.Create<Point>()), 0);

    while (true) {
        minPaths.TryDequeue(out PointWithVisited cur, out long min);
        if (cur.point.Equals(end)) {
            return min;
        }

        var adjacent = GetAdjacent(cur.point, cur.visited, caveToCheck);
        var nextVisited = cur.visited.Add(cur.point);
        foreach (var a in adjacent) {
            var riskLevel = min + caveToCheck[a.row, a.col];
            if (visitedLowest.ContainsKey(a) && visitedLowest[a] <= riskLevel) {
                continue;
            }
            visitedLowest[a] = riskLevel;
            minPaths.Enqueue(new PointWithVisited(a, nextVisited), riskLevel);
        }
    }
}

List<Point> GetAdjacent(Point cur, ImmutableHashSet<Point> visited, int[,] caveToCheck) {
    return new List<Point>() {
            new Point(cur.row + 1, cur.col),
            new Point(cur.row - 1, cur.col),
            new Point(cur.row, cur.col + 1),
            new Point(cur.row, cur.col - 1),
        }.Where(p => p.row >= 0 && p.row < caveToCheck.GetLength(0) && p.col >= 0 && p.col < caveToCheck.GetLength(1))
        .Where(p => !visited.Contains(p))
        .ToList();
}

record PointWithVisited(Point point, ImmutableHashSet<Point> visited);

record Point(int row, int col);
#endif