// #define Day25
#if Day25

var linesSplit = File.ReadAllLines("day25/input");

int rowMax = linesSplit.Length;
int colMax = linesSplit[0].Length;
var map = new char[linesSplit.Length, linesSplit[0].Length];
var easts = new List<Point>();
var souths = new List<Point>();

for (int row = 0; row < linesSplit.Length; row++) {
    for (int col = 0; col < linesSplit[0].Length; col++) {
        if (linesSplit[row][col] == '>') {
            map[row, col] = linesSplit[row][col];
            easts.Add(new Point(row, col));
        } else if (linesSplit[row][col] == 'v') {
            map[row, col] = linesSplit[row][col];
            souths.Add(new Point(row, col));
        }
    }
}

long step = 0;
bool moved = true;

while (moved) {
    moved = false;
    var nextMap = new char[linesSplit.Length, linesSplit[0].Length];
    var nextEasts = new List<Point>();
    var nextSouths = new List<Point>();
    foreach (var east in easts) {
        int checkCol = (east.col + 1) % colMax;
        if (map[east.row, checkCol] == '\0') {
            nextMap[east.row, checkCol] = '>';
            nextEasts.Add(new Point(east.row, checkCol));
            moved = true;
        } else {
            nextMap[east.row, east.col] = '>';
            nextEasts.Add(new Point(east.row, east.col));
        }
    }

    foreach (var south in souths) {
        int checkRow = (south.row + 1) % rowMax;
        if (nextMap[checkRow, south.col] == '\0' && map[checkRow, south.col] != 'v') {
            nextMap[checkRow, south.col] = 'v';
            nextSouths.Add(new Point(checkRow, south.col));
            moved = true;
        } else {
            nextMap[south.row, south.col] = 'v';
            nextSouths.Add(new Point(south.row, south.col));
        }
    }

    map = nextMap;
    easts = nextEasts;
    souths = nextSouths;
    step++;
}
Console.WriteLine(step);

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