d13p1 and d13p2

13/part1.pl

@@ -0,0 +1,44 @@
+:- use_module(library(pio)).
+:- initialization(main, main).
+
+main([FileName|_]) :-
+    input(FileName, Blocks),
+    convlist(vert_reflect, Blocks, Vs),
+    convlist(horz_reflect, Blocks, Hs),
+    sum_list(Vs, V),
+    sum_list(Hs, H),
+    Answer is 100*V + H,
+    writef('Answer=%t\n', [Answer]).
+
+vert_reflect(Block, N) :- reflect(Block, N).
+horz_reflect(Block, N) :- maplist({N}/[Row]>>(reflect(Row, N)), Block).
+
+reflect(Items, N) :- perfect_reflect(Items, N).
+reflect(Items, N) :-
+    append(SubItems, [_|_], Items),
+    perfect_reflect(SubItems, N).
+reflect(Items, N) :-
+    append(Prefix, SubItems, Items),
+    perfect_reflect(SubItems, SubN),
+    length(Prefix, Len), N is SubN + Len.
+
+% reflect right down the middle. N is half list length.
+perfect_reflect([A, A], 1).
+perfect_reflect(Items, N) :-
+    append([[Item], OtherItems, [Item]], Items),
+    perfect_reflect(OtherItems, N_sub1),
+    N is N_sub1 + 1.
+
+input(FileName, Blocks) :- phrase_from_file(blocks(Blocks), FileName).
+
+blocks([]) --> eos, !.
+blocks([Block|Blocks]) --> block(Block), blocks(Blocks).
+
+block([Line]) --> line(Line), ("\n"; eos), !.
+block([Line|Lines]) --> line(Line), block(Lines).
+
+line([]) --> ("\n"; eos), !.
+line([#|Chars]) --> "#", line(Chars).
+line([o|Chars]) --> ".", line(Chars).
+
+eos([], []).

13/part2.pl

@@ -0,0 +1,55 @@
+:- use_module(library(pio)).
+:- use_module(library(clpfd)).
+:- initialization(main, main).
+
+main([FileName|_]) :-
+    input(FileName, Blocks),
+    convlist(almost_reflect, Blocks, Vs), sum_list(Vs, V),
+    maplist(transpose, Blocks, TBlocks),
+    convlist(almost_reflect, TBlocks, Hs), sum_list(Hs, H),
+    Answer is 100*V + H,
+    writef('Answer=%t\n', [Answer]).
+
+almost_reflect(Items, N) :- almost_perfect_reflect(Items, N).
+almost_reflect(Items, N) :-
+    append(SubItems, [_|_], Items),
+    almost_perfect_reflect(SubItems, N).
+almost_reflect(Items, N) :-
+    append(Prefix, SubItems, Items),
+    almost_perfect_reflect(SubItems, SubN),
+    length(Prefix, Len), N is SubN + Len.
+
+almost_perfect_reflect([A, B], 1) :- diff(A, B, 1).
+almost_perfect_reflect(Items, N) :-
+    append([[A], OtherItems, [A]], Items),
+    almost_perfect_reflect(OtherItems, N_sub1),
+    N is N_sub1 + 1.
+almost_perfect_reflect(Items, N) :-
+    append([[A], OtherItems, [B]], Items),
+    diff(A, B, 1),
+    perfect_reflect(OtherItems, N_sub1),
+    N is N_sub1 + 1.
+
+% reflect right down the middle. N is half list length.
+perfect_reflect([A, A], 1).
+perfect_reflect(Items, N) :-
+    append([[Item], OtherItems, [Item]], Items),
+    perfect_reflect(OtherItems, N_sub1),
+    N is N_sub1 + 1.
+
+diff(L1, L2, N) :-
+    foldl([A, B, Prev, Curr]>>(Curr is Prev + abs(A - B)), L1, L2, 0, N).
+
+input(FileName, Blocks) :- phrase_from_file(blocks(Blocks), FileName).
+
+blocks([]) --> eos, !.
+blocks([Block|Blocks]) --> block(Block), blocks(Blocks).
+
+block([Line]) --> line(Line), ("\n"; eos), !.
+block([Line|Lines]) --> line(Line), block(Lines).
+
+line([]) --> ("\n"; eos), !.
+line([1|Chars]) --> "#", line(Chars).
+line([0|Chars]) --> ".", line(Chars).
+
+eos([], []).

13/test.txt

@@ -0,0 +1,15 @@
+#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#