Add day 2402.

lib/aoc.ml

@@ -0,0 +1,5 @@
+let nums_from_string s = List.map int_of_string (Str.split (Str.regexp " +") s)
+let distance1 a b = abs (a - b)
+
+let strings_from_file fname =
+  In_channel.with_open_text fname In_channel.input_lines

lib/aoc.mli

@@ -0,0 +1,10 @@
+val nums_from_string : string -> int list
+(** [nums_from_string s] takes a string of space separated integers and gives
+    back a list of the integers. *)
+
+val distance1 : int -> int -> int
+(** [distance1 a b] returns the absolute difference between [a] and [b]. *)
+
+val strings_from_file : string -> string list
+(** [strings_from_file fname] returns a list of strings from the file 
+    [fname].  Each string represents a line from the file. *)

lib/dune

@@ -0,0 +1,3 @@
+(library
+ (name aoc)
+ (libraries str))