static char[,] ExpandProblem(char[,] arr)
{
Span2D <char> insert = new char[, ]
{
{ ' ', ' ', '#', 'D', '#', 'C', '#', 'B', '#', 'A', '#', ' ', ' ' },
{ ' ', ' ', '#', 'D', '#', 'B', '#', 'A', '#', 'C', '#', ' ', ' ' },
};
var span = arr.AsSpan2D();
var expanded = new char[span.Height + 2, span.Width];
var expandedSpan = expanded.AsSpan2D();
span[0..3, ..].CopyTo(expandedSpan[0..3, ..]);
public Keypad(char[,] pad)
{
var span = pad.AsSpan2D();
var builder = ImmutableDictionary.CreateBuilder <Point2d, char>();
for (var y = 0; y < span.Height; y++)
{
var row = span.GetRowSpan(y);
for (var x = 0; x < row.Length; x++)
{
if (row[x] != ' ')
{
builder.Add(new Point2d(x, y), row[x]);
}
}
}
_keypad = builder.ToImmutable();
FiveKey = _keypad.Where(kvp => kvp.Value == '5').First().Key;
}