codewars: solve 'statistics' challenge

codewars/ocaml/rank-up/statistics-for-an-athletic-association/main.ml

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+let to_seconds (s : string) : int =
+  let raw_digits = String.split_on_char '|' s in
+  let digits = List.map (fun x -> (int_of_string x)) raw_digits in
+  List.fold_left (fun acc i -> (acc * 60 + i)) 0 digits;;
+
+let seconds_to_time (total_sec : int) : string =
+  let hours = total_sec / 3600 in
+  let minutes = (total_sec - hours * 3600) / 60 in
+  Printf.sprintf "%02d|%02d|%02d" hours minutes (total_sec - hours * 3600 - minutes * 60);;
+
+let range (l : int list) : int =
+  let min = List.fold_left Int.min Int.max_int l in
+  let max = List.fold_left Int.max 0 l in
+  max - min;;
+
+let avg (l : int list) : float =
+  let sum = List.fold_left Int.add 0 l in
+  (float_of_int sum) /. (float_of_int (List.length l));;
+
+let median (l : int list) : float =
+  let sorted = List.sort compare l in
+  let len = List.length l in
+  match len mod 2 with
+  | 0 -> float_of_int ((List.nth sorted (len / 2 - 1)) + (List.nth sorted (len / 2))) /. 2.0
+  | 1 -> float_of_int (List.nth sorted (len / 2))
+  | x -> 0.0;;
+
+let stat (s : string) : string =
+  match s with
+  | "" -> ""
+  | s -> (
+    let raw_results = List.map String.trim (String.split_on_char ',' s) in
+    let res_in_seconds = List.map to_seconds raw_results in
+  
+    let range_str = seconds_to_time (range res_in_seconds) in
+    let avg_str = seconds_to_time (int_of_float (avg res_in_seconds)) in
+    let median_str = seconds_to_time (int_of_float (median res_in_seconds)) in
+  
+    Printf.sprintf "Range: %s Average: %s Median: %s" range_str avg_str median_str
+  );;