Fibbonaci

open Hashtbl

let fib n=
        let wynik = Hashtbl.create n in
        let rec pom a b k =
                if k<=n then
                        begin
                                Hashtbl.add wynik b k;
                                pom b (a+b) (k+1);
                        end;
        in
        begin
                Hashtbl.add wynik 1 1;
                pom 1 1 2;
        end;
        wynik
let abs x =
        if x<0 then -x
        else x

let pred a b =
        if abs(a-b)=1 then true
        else if(a=2) then if abs(1-b)=1 then true
                          else false
        else if(b=2) then if abs(1-a)=1 then true
                          else false
        else false

let decision a b = if pred a b then max a b +1
                   else -1

let segment tab =
        let maxi = ref 0 in
        let n = Array.length tab in
        let fibtab = fib n in
        let dp = Array.make_matrix n n 0 in
        for i = 0 to (n-1) do
                let w = Hashtbl.find_opt fibtab tab.(i) in
                match w with
                |None -> (dp.(i).(i) <- (-1);)
                |Some w -> (dp.(i).(i) <- (w);)
        done;
        for x = 1 to n-1
        do
                for i=0 to n-1-x
                do
                        dp.(i).(i+x) <- decision dp.(i).(i+x-1) dp.(i+x).(i+x) ;
                        let cur = dp.(i).(i+x) in
                        if cur > !maxi then maxi:= cur;
                done;
        done;

        !maxi