Add day4

2 files changed, 49 insertions, 0 deletions

diff --git a/2023/ocaml/day4/bin/dune b/2023/ocaml/day4/bin/dune
new file mode 100644
index 0000000..add70da
--- /dev/null
+++ b/2023/ocaml/day4/bin/dune
@@ -0,0 +1,4 @@
+(executable
+ (public_name day4)
+ (name main)
+ (libraries day4))
diff --git a/2023/ocaml/day4/bin/main.ml b/2023/ocaml/day4/bin/main.ml
new file mode 100644
index 0000000..9d1a6ad
--- /dev/null
+++ b/2023/ocaml/day4/bin/main.ml
@@ -0,0 +1,45 @@
+let input_file = "input.txt"
+
+let read_file f =
+  let ic = open_in f in
+  try
+    let lines = really_input_string ic (in_channel_length ic) |> String.trim in
+    close_in ic;
+    lines
+  with e ->
+    close_in_noerr ic;
+    raise e
+
+let nums_from_string str =
+  String.split_on_char ' ' str
+  |> List.filter (fun ch -> String.length ch > 0)
+  |> List.map int_of_string
+
+let rec parse ?(result = 0) lines =
+  match lines with
+  | [] -> result
+  | x :: tail ->
+      let numbers =
+        List.nth (String.split_on_char ':' x) 1
+        |> String.split_on_char '|' |> List.map String.trim
+        |> List.map nums_from_string
+      in
+
+      let winnings = List.nth numbers 0 in
+      let plays = List.nth numbers 1 in
+
+      let k =
+        Int.shift_left 1
+          (List.length
+             (List.map
+                (fun win -> if List.mem win plays = true then 1 else 0)
+                winnings
+             |> List.filter (fun i -> i = 1))
+          - 1)
+      in
+
+      parse tail ~result:(result + k)
+
+let () =
+  let result = read_file input_file |> String.split_on_char '\n' |> parse in
+  Printf.printf "%d\n" result