Find the most frequent element from list.

lab15.pl

%% PACK SECTION
pack([X|Unpacked], Packed) :- pack(Unpacked, [[X]], Packed).

pack([H|T], [[H|Acc]|Rest], Packed) :- pack(T, [[H,H|Acc]|Rest], Packed).
pack([X|T], [[Y|Acc]|Rest], Packed) :-
    X \= Y,
    pack(T, [[X],[Y|Acc]|Rest], Packed).
pack([], RPacked, Packed) :- reverse(RPacked, Packed).

% UTILS SECTION

first([X], X).
first([H | _], H).
last([T], T).
last([_|T], X) :- last(T, X).


wich_bigger(L1,L2,L1) :- length(L1, L1Length), length(L2, L2Length), L1Length > L2Length.
wich_bigger(L1,L2,L2) :- length(L1, L1Length), length(L2, L2Length), L2Length >= L1Length.

find_winner([X], X).
find_winner([H | T], Res) :- find_winner(T, TEMP), wich_bigger(H, TEMP, Res).


perform(L, Times, Winner) :- msort(L, LSorted), pack(LSorted, LPacked), find_winner(LPacked, T), length(T, Times), first(T, Winner).
test(L, T) :- msort(L, LSorted), pack(LSorted, LPacked), find_winner(LPacked, T).