open W3q6h

(*lfreq_: value, list, freqCounter*)
let rec lfreq_ x l n = match l with
                    | hd::tl ->
                        if hd = x then
                            lfreq_ x tl n+1
                        else
                            lfreq_ x tl n
                    | _ -> n

(*lfreq: value, list*)
let lfreq x l = lfreq_ x l 0

(*delete_: value, inList, outList*)
let rec delete_ x li lo = match li with
                    | hd::tl ->
                        if hd != x then
                            delete_ x tl (hd::lo)
                        else
                            delete_ x tl lo
                    | _ -> lo (*removed reverse - not needed here*)

(*delete: value, list*)
let delete x l = delete_ x l []

(*freq_: list, element, elementFreq*)
let rec freq_ l e ef = match l with
                | hd::tl ->
                            let cef = lfreq hd l in
                            if cef > ef then
                                freq_ (delete hd l) hd cef
                            else
                                freq_ (delete hd l) e ef
                | _ -> e

(*freq: list*)
(*Returns the most frequent element in the list*)
let freq l = freq_ l 0 0

let _ = test freq