public static IEnumerable <(int, int)> Calculate(int[,] matrix)
{
for (var row = 0; row < matrix.RowCount(); row++)
{
for (var col = 0; col < matrix.ColumnCount(); col++)
{
if (IsSaddlePoint(row, col))
{
yield return(row + 1, col + 1);
}
}
}
bool IsSaddlePoint(int row, int col)
{
var value = matrix[row, col];
return(matrix.Row(row).All(n => n <= value) &&
matrix.Column(col).All(n => n >= value));
}
}