d10p1

10/part1.naive.pl

@@ -0,0 +1,98 @@
+% :- table valid/1.
+:- table path/3.
+
+answer(Answer) :-
+    pipe_at(From, ess),
+    once(path(From, Via, From)),
+    length(Via, ViaLen),
+    writef('%t -> %t\n', [From, Via]),
+    Answer is (ViaLen + 1) div 2 .
+
+% path(From, Next, To, Dist) :-
+%     pipe_at(From, FromPipe),
+%     FromG =.. [FromPipe, From, Next
+
+path(From, [Via], To) :-
+    pipe_at(Via, ViaPipe),
+    ViaG =.. [ViaPipe, Via, From, To], ViaG.
+
+path(From, [Via1, Via2 | Vias], To) :-
+    path(From, [Via1], Via2), 
+    path(Via1, [Via2 | Vias], To).
+
+dot(_, _, _) :- fail.
+    
+vert(X-Y, X1-Y, X2-Y) :-
+    pipe_at(X-Y, vert),
+    (   X1 is X+1, X2 is X-1
+    ;   X1 is X-1, X2 is X+1),
+    valid(X1-Y), valid(X2-Y).
+
+horz(X-Y, X-Y1, X-Y2) :-
+    pipe_at(X-Y, horz),
+    (   Y1 is Y+1, Y2 is Y-1
+    ;   Y1 is Y-1, Y2 is Y+1),
+    valid(X-Y1), valid(X-Y2).
+
+el(X-Y, X1-Y1, X2-Y2) :-
+    pipe_at(X-Y, el),
+    (   Y1 = Y, X1 is X-1, Y2 is Y+1, X2 = X
+    ;   X1 = X, Y1 is Y+1, X2 is X-1, Y2 = Y),
+    valid(X1-Y1), valid(X2-Y2).
+
+jay(X-Y, X1-Y1, X2-Y2) :-
+    pipe_at(X-Y, jay),
+    (   Y1 = Y, X1 is X-1, Y2 is Y-1, X2 = X
+    ;   X1 = X, Y1 is Y-1, X2 is X-1, Y2 = Y),
+    valid(X1-Y1), valid(X2-Y2).
+
+seven(X-Y, X1-Y1, X2-Y2) :-
+    pipe_at(X-Y, seven),
+    (   Y1 = Y, X1 is X+1, Y2 is Y-1, X2 = X
+    ;   X1 = X, Y1 is Y-1, X2 is X+1, Y2 = Y),
+    valid(X1-Y1), valid(X2-Y2).
+
+eff(X-Y, X1-Y1, X2-Y2) :-
+    pipe_at(X-Y, eff),
+    (   Y1 = Y, X1 is X+1, Y2 is Y+1, X2 = X
+    ;   X1 = X, Y1 is Y+1, X2 is X+1, Y2 = Y),
+    valid(X1-Y1), valid(X2-Y2).
+
+ess(X-Y, X1-Y1, X2-Y2) :-
+    pipe_at(X-Y, ess),
+    findall(Coord, ess_adjacent(Coord), [X1-Y1, X2-Y2]).
+
+ess_adjacent(X1-Y1) :-
+    pipe_at(X-Y, ess),
+    (   X1 is X-1, Y1 = Y, pipe_at(X1-Y1, El), points_down(El)
+    ;   X1 = X, Y1 is Y+1, pipe_at(X1-Y1, El), points_left(El)
+    ;   X1 is X+1, Y1 = Y, pipe_at(X1-Y1, El), points_up(El)
+    ;   X1 = X, Y1 is Y-1, pipe_at(X1-Y1, El), points_right(El)),
+    valid(X1-Y1).
+
+points_down(El) :- (El=ess; El=vert; El=seven; El=eff).
+points_left(El) :- (El=ess; El=horz; El=jay; El=seven).
+points_up(El) :- (El=ess; El=vert; El=el; El=jay).
+points_right(El) :- (El=ess; El=horz; El=el; El=eff).
+
+valid(X-Y) :-
+    input(Map), length(Map, NRows),
+    Map = [Row0 | _], length(Row0, NCols),
+    X >= 0, Y >= 0,
+    X < NRows, Y < NCols.
+
+% Element is at (Row, Column) in the map.
+pipe_at(Row-Column, Element) :-
+    input(Map),
+    nth0(Row, Map, SubList),
+    nth0(Column, SubList, Symbol),
+    symbol_predicate(Symbol, Element).
+
+symbol_predicate("|", vert).
+symbol_predicate("-", horz).
+symbol_predicate("L", el).
+symbol_predicate("J", jay).
+symbol_predicate("7", seven).
+symbol_predicate("F", eff).
+symbol_predicate(".", dot).
+symbol_predicate("S", ess).