Day 1: the camel

AdventOfCode2024/bin/dune

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+(executable
+ (public_name AdventOfCode2024)
+ (name main)
+ (libraries AdventOfCode2024))

AdventOfCode2024/bin/main.ml

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+open Scanf
+
+let read_lines name =
+  let ic = open_in name in
+  let try_read () =
+    try Some (input_line ic) with End_of_file -> None in
+  let rec loop acc = match try_read () with
+    | Some s -> loop (s :: acc)
+    | None -> close_in ic; List.rev acc in
+  loop []
+
+let handle_line line =
+    sscanf line "%d   %d" (fun num1 num2 -> (num1, num2))
+
+let sort_list l =
+    List.sort compare l
+
+let build_lists lines =
+    let rec loop lines l1 l2 = match lines with
+        | [] -> (l1, l2)
+        | head :: tail -> 
+            let (num1, num2) = handle_line head in
+            loop tail (l1 @ [num1]) (l2 @ [num2]) in
+    loop lines [] [] |> (fun (l1, l2) -> (sort_list l1, sort_list l2))
+
+let find_occurances l item =
+    let rec loop l item acc = match l with
+        | [] -> acc
+        | head :: tail -> if head == item then loop tail item (acc + 1) else loop tail item acc in
+    loop l item 0
+
+let () = 
+    print_endline "\nAdvent of Code 2024";
+    let lines = read_lines "./bin/input.txt" in
+
+    let rec distance l1 l2 acc =
+        match (l1, l2) with
+            | ([], []) -> acc
+            | (h1 :: t1, h2 :: t2) ->
+                distance t1 t2 (acc + if h1 > h2 then h1 - h2 else h2 - h1)
+            | _, _ -> acc in
+
+    let (l1, l2) = build_lists lines in
+    let part1 = distance l1 l2 0 in
+    Printf.printf "Part 1: %s\n" (string_of_int part1);
+
+    let rec similarity l1 l2 acc =
+        match l1 with
+            | [] -> acc
+            | head :: tail -> similarity tail l2 (acc + head * find_occurances l2 head) in
+    
+    let part2 = similarity l1 l2 0 in
+    Printf.printf "Part 2: %s\n" (string_of_int part2);