// Complete the maxRegion function below.
static int maxRegion(int[][] matrix)
{
var xOffset = new[] { -1, 0, 1, -1 };
var yOffset = new[] { -1, -1, -1, 0 };
var ds = new DisjointSets();
var rows = matrix.Length;
var cols = matrix[0].Length;
var max = 0;
Func <int, int, bool> isValid = (int x, int y) =>
{
return(x >= 0 && x < cols && y >= 0 && y < rows);
};
for (int y = 0; y < rows; y++)
{
for (int x = 0; x < cols; x++)
{
if (matrix[y][x] == 0)
{
continue;
}
var current = new CellKey(x, y);
ds.AddNew(current);
max = Math.Max(max, 1);
for (int index = 0; index < xOffset.Length; index++)
{
var ox = x + xOffset[index];
var oy = y + yOffset[index];
if (!isValid(ox, oy))
{
continue;
}
if (matrix[oy][ox] == 0)
{
continue;
}
var offset = new CellKey(ox, oy);
if (ds.Find(current) != ds.Find(offset))
{
max = Math.Max(max, ds.Union(current, offset));
}
}
}
}
return(max);
}