actual proper d8p2

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Dory 2023-12-08 20:21:08 -08:00
parent d9980e3b33
commit bdf5fe807a

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08/part2.pl Normal file
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:- table direction_loop/1.
:- op(700, xfx, l).
:- op(700, xfx, r).
From l To :- From to To-_.
From r To :- From to _-To.
answer(Answer) :-
starts(Starts),
routes(Starts, Routes),
collapse_routes(Routes, _-(Answer-_-_)).
collapse_routes([X], X).
collapse_routes(Routes, Collapsed) :-
sort(2, @=<, Routes, [Route1, Route2 | CdrRoutes]),
unify2(Route1, Route2, 0-0-0-0, [], NewRoute),
collapse_routes([NewRoute | CdrRoutes], Collapsed).
unify2(Route1, Route2, N1-Term1-N2-Term2, Founds, NewRoute) :-
Route1 = A1-(Stride1-Offset1-Loop1),
Route2 = A2-(Stride2-Offset2-Loop2),
nth0(Term1, Loop1, C1-_),
nth0(Term2, Loop2, C2-_),
Z1 is Offset1 + Stride1*N1 + C1,
Z2 is Offset2 + Stride2*N2 + C2,
next(Route1, N1-Term1, NextN1-NextTerm1),
( Z1 =:= Z2
-> ( Founds = [OldZ]
-> atom_concat(A1, A2, NewA),
NewStride is Z1 - OldZ,
NewRoute = NewA-(NewStride-OldZ-[0-NewA]),
!
; unify2(Route1, Route2, NextN1-NextTerm1-N2-Term2, [Z1], NewRoute)
)
; Z1 < Z2
-> unify2(Route1, Route2, NextN1-NextTerm1-N2-Term2, Founds, NewRoute)
; next(Route2, N2-Term2, NextN2-NextTerm2),
unify2(Route1, Route2, N1-Term1-NextN2-NextTerm2, Founds, NewRoute)
).
next(_-(_-_-Loop), NLoops-Term, NextNLoops-NextTerm) :-
length(Loop, LoopLen),
( Term < LoopLen - 1
-> NextNLoops is NLoops, NextTerm is Term + 1
; NextNLoops is NLoops + 1, NextTerm is 0).
routes(Starts, Routes) :-
maplist([S, S-Route]>>(zloop([], S, 0, [], Route)), Starts, Routes).
zloop(_, _, _, Zs, Stride-Offset-Loop) :-
Zs = [FirstZIndex-Z | _], reverse(Zs, [LastZIndex-Z | ReversedZs]),
DeltaZ is LastZIndex - FirstZIndex, DeltaZ =\= 0,
direction_len(Len),
divmod(DeltaZ, Len, _, 0),
Offset = FirstZIndex, Stride = DeltaZ,
foldl([Idx-Z, NewIdx-Z, Off, Off]>>(NewIdx is Idx - Off),
ReversedZs, ReversedLoop, Offset, _),
reverse(ReversedLoop, Loop),
!.
zloop(Directions, Node, Index, Zs, Route) :-
( is_end(Node)
-> append(Zs, [Index-Node], NewZs)
; NewZs = Zs
),
next_step(Directions, Move, Remain),
G =.. [Move, Node, To], G,
NewIndex is Index + 1,
zloop(Remain, To, NewIndex, NewZs, Route).
starts(Starts) :- findall(X, X to _, Nodes), include(is_start, Nodes, Starts).
is_start(Node) :- atom_chars(Node, [_, _, a]).
is_end(Node) :- atom_chars(Node, [_, _, z]).
next_step([Move | Remain], Move, Remain).
next_step([], Move, Remain) :- direction_list([Move | Remain]).
direction_list(Dir) :- direction(Str), atom_chars(Str, Dir).
direction_len(Len) :- direction_list(D), length(D, Len).