2025: day 5: ocaml again!

AdventOfCode2025/day5/bin/dune

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+(executable
+ (public_name day5)
+ (name main)
+ (libraries day5))

AdventOfCode2025/day5/bin/main.ml

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+let get_range str =
+    let list = (String.split_on_char '-' str) 
+        |> List.map int_of_string in
+
+    assert (List.length list == 2);
+    
+    let lower = List.nth list 0 in
+    let upper = List.nth list 1 in
+
+    (lower, upper)
+
+let is_item_in_range  i (lower, upper) = 
+    lower <= i && i <= upper
+
+let rec list_some l fn = 
+    match l with 
+    | [] -> false
+    | head :: tail -> if fn head then true else list_some tail fn
+
+let is_item_in_ranges ranges i =
+    list_some ranges (is_item_in_range i)
+
+
+let is_overlapping (lower1, upper1) (lower2, upper2) =
+    lower1 <= lower2 && lower2 <= upper1 ||
+    lower2 <= lower1 && lower1 <= upper2
+
+let get_combined_ranges (lower1, upper1) (lower2, upper2) =
+    let lower = min lower1 lower2 in
+    let upper = max upper1 upper2 in
+    (lower, upper)
+
+let non_overlapping_ranges_work ranges =
+    let rec loop acc changes ranges =
+        match ranges with 
+        | [] -> (acc, changes)
+        | head :: tail -> 
+            let overlap_fn = is_overlapping head in
+            let overlapping_index = List.find_index overlap_fn tail in
+            match overlapping_index with
+            | Some r -> 
+                let (l, u) = List.nth tail r in
+                let tail_without_index = List.filter 
+                    (fun (lower, upper) -> not (lower == l && upper == u)) tail in
+                let combined_range = get_combined_ranges head (l, u) in
+                loop (combined_range :: acc) true (tail_without_index)
+            | None -> loop (head :: acc) changes tail
+    in
+    loop [] false ranges
+
+(* let rec print_ranges l = *)
+(*     match l with  *)
+(*     | [] -> print_endline ""; *)
+(*     | (lower, upper) :: tail ->  *)
+(*         Printf.printf "lower=%d,upper=%d\n" lower upper; *)
+(*         print_ranges tail *)
+        
+
+let rec non_overlapping_ranges ranges =
+    let (ranges, changes)  = non_overlapping_ranges_work ranges in
+    if changes then non_overlapping_ranges ranges
+    else ranges
+
+    
+let solve lines = 
+    let no_empty_lines = List.filter (fun i -> String.length i > 0) lines in
+    let (ranges, items) = List.partition (fun i -> String.contains i '-') no_empty_lines in
+
+    let ranges = List.map get_range ranges in
+    let items = List.map int_of_string items in
+
+    let part1 = List.fold_left (
+        fun acc i -> if is_item_in_ranges ranges i then acc + 1 else acc
+    ) 0 items in
+
+    let ranges = non_overlapping_ranges ranges in
+     
+    let part2 = List.fold_left (
+        fun acc (lower, upper) -> acc + (upper - lower + 1)
+    ) 0 ranges in
+
+    (part1, part2)
+
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+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 () =
+print_endline "Day 5";
+  let part1, part2 =
+    read_lines "./input.txt" |> solve
+  in
+  Printf.printf "Part 1: %s\nPart 2: %s\n" (string_of_int part1)
+    (string_of_int part2)
+
+