feat(2025d4p1): add code to convert input into a matrix and pp the matrix

1 files changed, 39 insertions, 1 deletions

diff --git a/2025/ocaml/lib/application/d04p01.ml b/2025/ocaml/lib/application/d04p01.ml
index 26319df..85b0bbf 100644
--- a/2025/ocaml/lib/application/d04p01.ml
+++ b/2025/ocaml/lib/application/d04p01.ml
@@ -1 +1,39 @@
-let solve _ () = failwith "not started"
+(** [input_to_matrix input] is a 2D Array where each line of the [input] is
+    a row and each character in that line is a column.
+    Requires: all lines in input are of equal length. *)
+let input_to_matrix input =
+  let lines =
+    input |> String.split_on_char '\n'
+    |> List.filter_map (fun line ->
+        let trimmed = String.trim line in
+        if trimmed <> "" then Some trimmed else None )
+  in
+  let row_count = List.length lines in
+  let column_count =
+    match List.nth_opt lines 1 with
+    | None ->
+        failwith "first line should not be empty"
+    | Some line ->
+        String.length line
+  in
+  let matrix = Array.make_matrix column_count row_count "" in
+  List.iteri
+    (fun x line ->
+      String.iteri (fun y char -> matrix.(x).(y) <- Char.escaped char) line )
+    lines ;
+  matrix
+
+let pp_matrix matrix =
+  "[\n"
+  ^ ( matrix
+    |> Array.map @@ Array.fold_left (fun acc c -> acc ^ c) ""
+    |> Array.fold_left
+         (fun acc line ->
+           if acc = "" then "  [" ^ line ^ "]" else acc ^ "\n  [" ^ line ^ "]" )
+         "" )
+  ^ "\n]"
+
+let solve input () =
+  let matrix = input |> input_to_matrix in
+  Logs.debug (fun m -> m "%s" @@ pp_matrix matrix) ;
+  0