let rec rapikan = function
| [] -> []
| [(p, k)] -> if k = 0.0 then [] else [(p, k)]
| (p1, k1)::(p2, k2)::t -> if p1 = p2 then
                               if k1+k2 = 0.0 then rapikan t
                               else (p1, k1+k2)::rapikan t
                           else
                               if k1 = 0.0 then rapikan ((p2, k2)::t)
                               else (p1, k1)::rapikan ((p2, k2)::t);;

let normalisasi a = rapikan (List.rev(List.sort a));;