23/part2.pl

@@ -1,90 +0,0 @@
-:- use_module(library(pio)).
-:- use_module(library(dcg/basics)).
-:- initialization(main, main).
-:- op(700, xfx, is_key_of).
-
-main([FileName|_]) :-
-    input(FileName, Map, Start, End),
-    graph(Map, Start, End, Graph),
-    StartKey is_key_of Start, EndKey is_key_of End,
-    findall(Dist, walk(Graph, visited{}, StartKey, EndKey, Dist), Dists),
-    max_list(Dists, Answer),
-    write(Answer), nl.
-
-walk(_, _, Node, Node, 0).
-walk(Graph, Visited, Start, End, Dist) :-
-    member(Next-NextDist, Graph.get(Start)), \+ _ = Visited.get(Next),
-    NextVisited = Visited.put(Next, true),
-    walk(Graph, NextVisited, Next, End, RemainingDist),
-    Dist is NextDist + RemainingDist.
-    
-graph(Map, Start, End, Graph) :-
-    branch_points(Map, Branches), Nodes = [Start, End|Branches],
-    findall(
-        Key-Dists,
-        (   member(Node, Nodes),
-            dists_from(Map, Nodes, Node, Dists),
-            Key is_key_of Node),
-        GraphList),
-    dict_pairs(Graph, edge, GraphList).
-        
-branch_points(Map, Points) :- findall(Point, branch_point(Map, Point), Points).
-branch_point(Map, X-Y) :-
-    nth1(X, Map, Row), nth1(Y, Row, Cell), Cell = '.',
-    findall(X1-Y1, cell_neighbor(Map, 0-0, X-Y, X1-Y1), Neighbors),
-    length(Neighbors, N), N > 2.
-
-dists_from(Map, Nodes, N1, Dists) :-
-    findall(
-        Key-Dist, (
-            member(N2, Nodes), \+ N1 = N2,
-            nobranch_dist(Map, 0-0, N1, N2, Dist),
-            Key is_key_of N2),
-        Dists).
-
-is_key_of(Key, X-Y) :- Key is X*1000 + Y.
-    
-% nobranch_dist(X1-Y1, X2-Y2, Dist) :- true.
-nobranch_dist(_, _, X-Y, X-Y, 0).
-nobranch_dist(Map, FromX-FromY, X1-Y1, X2-Y2, Dist) :-
-    findall(Xn-Yn, cell_neighbor(Map, FromX-FromY, X1-Y1, Xn-Yn), Neighbors),
-    length(Neighbors, NeighborCount),
-    \+ (NeighborCount =\= 1, FromX =\= 0),  % on a route or at beginning
-    member(Neighbor, Neighbors),
-    nobranch_dist(Map, X1-Y1, Neighbor, X2-Y2, NextDist),
-    Dist is NextDist + 1.
-    
-% cell_neighbor finds an adjacent neighbor
-cell_neighbor(Map, FromX-FromY, X-Y, X1-Y1) :-
-    (   X1 is X + 1, Y1 = Y;
-        X1 is X - 1, Y1 = Y;
-        X1 = X, Y1 is Y + 1;
-        X1 = X, Y1 is Y - 1
-    ),
-    nth1(X1, Map, Row1), nth1(Y1, Row1, '.'),
-    \+ (X1 = FromX, Y1 = FromY).
-
-% input parsing stuff below. Brick indexing is for debugging.
-input(FileName, Map, 1-StartY, EndX-EndY) :-
-    phrase_from_file(lines(Map), FileName),
-    length(Map, EndX),
-    nth1(1, Map, StartRow), nth1(StartY, StartRow, '.'),
-    nth1(EndX, Map, EndRow), nth1(EndY, EndRow, '.').
-
-lines([]) --> eos, !.
-lines([Line|Lines]) --> line(Line), lines(Lines).
-
-line([]) --> ("\n"; eos), !.
-line(['#'|Chars]) --> "#", line(Chars).
-line(['.'|Chars]) --> ("."; ">"; "v"), line(Chars).
-
-% debug
-print(Map) :-
-    findall(
-        X,
-        (   nth1(X, Map, Line),
-            format('~3d', [X]), write(" "),
-            atomic_list_concat(Line, Str), write(Str), nl
-        ),
-        _),
-    nl.