prison_notfinished

-module(solution).
-export([main/0]).

pairs_is_equal([X,Y],[P,Q]) ->
    P==X orelse Q==X orelse P == Y orelse Q==Y.
main() ->
    {ok,[Count]}=io:fread("","~d"),
    {ok,[CountPairs]}=io:fread("","~d"),
    Set=sets:new(),
    main(CountPairs,Set).

main(CountPairs,Set) when CountPairs ==0 ->
    parse_set(sets:new(),Set,sets:to_list(Set));
main(CountPairs,Set) when CountPairs /=0 ->
    {ok,[P,Q]}=io:fread("","~d~d"),
    NewSet=sets:add_element([P,Q],Set),
    main(CountPairs-1,NewSet).

parse_set(Set,Sorted,[]) ->
    io:format("End~p~n",[sets:to_list(Set)]);

parse_set(New,Set,[H|Tail]) ->
    PromData=sets:filter(fun(Elem) -> pairs_is_equal(Elem,H) end,Set),
    Data=parse_subset(sets:to_list(PromData),Set),
    io:format("Data~p~n",[sets:to_list(Data)]),
    case sets:size(Data) > 0 of
    true -> SortedSet=sets:subtract(Set,Data),
        NewSet=sets:add_element(Data,New),
        parse_set(NewSet,SortedSet,Tail);
    false -> parse_set(New,Set,Tail)
    end.