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-module(problem41).
-export([solve/0]).
solve() ->
Pan = gen_perms(),
Pri = gen_primes([2,3]),
lists:max([X || X <- Pan, lists:member(X, Pri)]).
gen_perms() -> [list_to_integer(X) || X <- perms("123456789")].
perms([]) -> [[]];
perms(L) -> [[H|T] || H <- L, T <- perms(L--[H])].
gen_primes(L) ->
if
hd(L) > 987654321 ->
tl(L);
true ->
gen_primes(gen_next(L))
end.
gen_next(List) ->
gen_next(List, lists:max(List) + 1).
gen_next(List, Next) ->
Q = will_divide(Next, List),
if
Q ->
gen_next(List, Next + 1);
true ->
[Next|List]
end.
will_divide(_, []) ->
false;
will_divide(Num, [H|T]) ->
if
Num rem H =:= 0 ->
true;
true ->
will_divide(Num, T)
end.
|
