1 parse_input(File) :-
2     read_file_to_string(File, Content, []),
3     split_string(Content, "\n", "", Lines0),
4     exclude(=(""), Lines0, Lines),
5     maplist(assert_line, Lines).
6 
7 assert_device_output(Device, Output) :-
8     assertz(device_output(Device, Output)).
9 
10 assert_line(Line) :-
11     split_string(Line, ": ", "", Parts),
12     [Device, _ | Outputs] = Parts,
13     maplist(assert_device_output(Device), Outputs).
14 
15 sum_pairs([], 0, 0).
16 sum_pairs([[A, B] | Rest], SumA, SumB) :-
17     sum_pairs(Rest, RestSumA, RestSumB),
18     SumA is RestSumA + A,
19     SumB is RestSumB + B.
20 
21 :- dynamic cached_result/4.
22 
23 paths("out", Dac/Fft, 1, Task2) :-
24     Dac == seen,
25     Fft == seen
26     -> Task2 = 1
27     ;  Task2 = 0.
28 
29 paths(Current, Flags, Task1, Task2) :-
30     cached_result(Current, Flags, Task1, Task2), !.
31 
32 paths(Current, Dac/Fft, Task1, Task2) :-
33     ((Dac == seen ; Current == "dac") -> Dac1 = seen ; Dac1 = unseen),
34     ((Fft == seen ; Current == "fft") -> Fft1 = seen ; Fft1 = unseen),
35     findall([Task1, Task2], (device_output(Current, Next),
36                              paths(Next, Dac1/Fft1, Task1, Task2)),
37             Pairs),
38     sum_pairs(Pairs, Task1, Task2),
39     assertz(cached_result(Current, Dac/Fft, Task1, Task2)).
40 
41 paths(Current, Task1, Task2) :-
42     paths(Current, unseen/unseen, Task1, Task2).
43 
44 :-
45     parse_input("input/11.txt"),
46     paths("you", Task1, _),
47     paths("svr", _, Task2),
48     format("~d ~d~n", [Task1, Task2]).