discussion
Same, except in 4-1 I used a recursive function to traverse each direction according to the offset decided by the selected direction (like SW is row++,col--) , due to functional programming induced brain damage.
Would have been pretty useful too if 4-2 turned out to be about finding longer patterns, instead of smaller and in half the directions.
4-1
Inlined some stuff to fit everything in one function:
let rec isXmas (row:int) (col:int) (dir:int) (depth:int) (arr: char array2d) : bool =
let value = arr.[row,col]
if depth = 3
then value = 'S'
else if [|'X';'M';'A';'S'|].[depth] = value
then
let (nextRow, nextCol) =
match dir with
| 1 -> row + 1, col - 1
| 2 -> row + 1, col
| 3 -> row + 1, col + 1
| 4 -> row, col - 1
| 6 -> row, col + 1
| 7 -> row - 1, col - 1
| 8 -> row - 1, col
| 9 -> row - 1, col + 1
| _ -> failwith $"{dir} isn't a numpad direction."
let rowCount = arr |> Array2D.length1
let colCount = arr |> Array2D.length2
if nextRow >= 0 && nextRow < rowCount && nextCol >= 0 && nextCol < colCount
then isXmas nextRow nextCol dir (depth+1) arr
else false
else false
Then you run this for every appropriately pruned 'X' times every direction and count the trues.