// Find monsters by rotating/flipping until some are found
// Rotate the monster instead of the map, as it's cheaper
static bool FindWaterRoughness(char[,] map, char[,] monster, ref int roughness)
{
var mapw = map.GetLength(0);
var maph = map.GetLength(1);
var monw = monster.GetLength(0);
var monh = monster.GetLength(1);
var xscan = mapw - monw;
var yscan = maph - monh;
var monsterspots = monster.PositionsOf('#');
var monsters = 0;
// Scan map for occurrences of the monster (don't care about overlaps)
for (var x = 0; x < xscan; x++)
{
for (var y = 0; y < yscan; y++)
{
if (monsterspots.All(p => map[x + p.X, y + p.Y] == '#'))
{
monsters++;
}
}
}
if (monsters == 0)
{
return(false);
}
roughness = map.CountChar('#') - monsters * monsterspots.Count();
return(true);
}