public static int Solve(string[] input)
{
List <List <GridTile> > grid = input.Select(r => r.Select(c => GridTileExtensions.CharToGrid(c)).ToList()).ToList();
List <List <GridTile> > newGrid = null;
int rounds = 0;
int numberOfChanges = -1;
while (numberOfChanges != 0)
{
++rounds;
numberOfChanges = 0;
newGrid = grid.Clone2DList();
Enumerable.Range(0, grid.Count).AsParallel().ForAll(y => {
for (int x = 0; x < grid[y].Count; ++x)
{
if (grid[y][x] != GridTile.Floor)
{
int occupiedSeatsNeighbouring = 0;
foreach (var func in new Func <int, int, (int x, int y)>[] {
(x, y) => (x - 1, y - 1),
(x, y) => (x, y - 1),
(x, y) => (x + 1, y - 1),
(x, y) => (x - 1, y),
(x, y) => (x + 1, y),
(x, y) => (x - 1, y + 1),
(x, y) => (x, y + 1),
(x, y) => (x + 1, y + 1),
})
public static int Solve(string[] input)
{
List <List <GridTile> > grid = input.Select(r => r.Select(c => GridTileExtensions.CharToGrid(c)).ToList()).ToList();
List <List <GridTile> > newGrid = null;
int rounds = 0;
int numberOfChanges = -1;
while (numberOfChanges != 0)
{
++rounds;
numberOfChanges = 0;
newGrid = grid.Clone2DList();
Enumerable.Range(0, grid.Count).AsParallel().ForAll(y => {
for (int x = 0; x < grid[y].Count; ++x)
{
if (grid[y][x] != GridTile.Floor)
{
int occupiedSeatsNeighbouring = 0;
foreach (int yOffset in new[] { -1, 0, 1 })
{
foreach (int xOffset in new[] { -1, 0, 1 })
{
if (x + xOffset >= 0 && x + xOffset < grid[y].Count && y + yOffset >= 0 && y + yOffset < grid.Count && (xOffset != 0 || yOffset != 0))
{
if (grid[y + yOffset][x + xOffset] == GridTile.OccupiedSeat)
{
++occupiedSeatsNeighbouring;
}
}
}
}
if (grid[y][x] == GridTile.EmptySeat && occupiedSeatsNeighbouring == 0)
{
newGrid[y][x] = GridTile.OccupiedSeat;
++numberOfChanges;
}
else if (grid[y][x] == GridTile.OccupiedSeat && occupiedSeatsNeighbouring >= 4)
{
newGrid[y][x] = GridTile.EmptySeat;
++numberOfChanges;
}
}
}
});
grid = newGrid;
}
return(grid.Sum(r => r.Sum(c => c == GridTile.OccupiedSeat ? 1 : 0)));
}