1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
-module(problem3).
-export([solve/0]).
solve() -> whittle(600851475143,[2,3,5,7,11,13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97],1).
whittle(Num,List,Max) ->
Q = will_divide(Num, List),
if
Num =:= 1 ->
Max;
Q ->
H = which_divides(Num,List),
if
H > Max ->
whittle(Num div H, List, H);
true ->
whittle(Num div H, List, Max)
end;
true ->
whittle(Num, gen_next(List), Max)
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 ->
List ++ [Next]
end.
will_divide(_, []) ->
false;
will_divide(Num, [H|T]) ->
if
Num rem H =:= 0 ->
true;
true ->
will_divide(Num, T)
end.
which_divides(Num, [H|T]) ->
if
Num rem H =:= 0 ->
H;
true ->
which_divides(Num, T)
end.
|
