void DfsBorder(int[,] grid, int row, int col, bool[,] visited, VirusRegion reg)
{
int m = grid.GetLength(0);
int n = grid.GetLength(1);
visited[row, col] = true;
foreach (var dir in Dirs)
{
int r = row + dir[0];
int c = col + dir[1];
if (0 <= r && r < m && 0 <= c && c < n)
{
if (grid[r, c] == 0)
{
reg.WallCount++;
reg.Borders.Add(r * m + c);
}
if (grid[r, c] == 1 && !visited[r, c])
{
DfsBorder(grid, r, c, visited, reg);
}
}
}
}
public int ContainVirus(int[,] grid)
{
int ret = 0;
int m = grid.GetLength(0);
int n = grid.GetLength(1);
while (true)
{
// find the virus region with max border
var maxreg = new VirusRegion(0, 0);
var visited = new bool[m, n];
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
if (grid[i, j] == 1 && !visited[i, j])
{
var reg = new VirusRegion(i, j);
DfsBorder(grid, i, j, visited, reg);
if (maxreg.Borders.Count < reg.Borders.Count)
{
maxreg = reg;
}
}
}
}
if (maxreg.Borders.Count == 0)
{
break;
}
// create the wall to quarantine this max region
ret += maxreg.WallCount;
DfsWall(grid, maxreg.Row, maxreg.Col);
// infect all border
var newInfected = new bool[m, n];
for (int i = 0; i < m; i++)
{
for (int j = 0; j < n; j++)
{
if (grid[i, j] == 1 && !newInfected[i, j])
{
foreach (var dir in Dirs)
{
int r = i + dir[0];
int c = j + dir[1];
if (0 <= r && r < m && 0 <= c && c < n && grid[r, c] == 0)
{
grid[r, c] = 1;
newInfected[r, c] = true;
}
}
}
}
}
}
return(ret);
}
