d12p1

12/part1.pl

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+:- use_module(library(pio)).
+:- use_module(library(dcg/basics)).
+:- initialization(main, main).
+
+main([FileName | _]) :-
+    input(FileName, Lines),
+    foldl([Line, Prev, Curr]>>(count_resolutions(Line, N), Curr is Prev + N), Lines, 0, Ns),
+    writef('Res=%w\n', [Ns]).
+
+count_resolutions(Line-Bads, N) :-
+    writef('Resolving %w\n', [Line-Bads]),
+    findall(Res, resolve(Line, Bads, Res), Resolutions),
+    length(Resolutions, N).
+    
+% Bads is list of contiguous blocks of bad items in Xs; w/unks resolved in Ys.
+resolve([], [], []).
+resolve([good|Xs], Bads, [good|Ys]) :- resolve(Xs, Bads, Ys).
+resolve([unk|Xs], Bads, Ys) :-
+    resolve([good|Xs], Bads, Ys);
+    resolve([bad|Xs], Bads, Ys).
+resolve([bad|Xs], [N|Bads], Ys) :-
+    length(BadsUnks, N),
+    (Next = good; Next = unk),
+    append(BadsUnks, [Next|RemainingXs], [bad|Xs]),
+    bads_or_unks(BadsUnks),
+    resolve([good|RemainingXs], Bads, RemainingYs),
+    nbads(BadRun, N), append(BadRun, RemainingYs, Ys).
+
+% List contains all bads or unks
+bads_or_unks([]).
+bads_or_unks([bad|List]) :- bads_or_unks(List).
+bads_or_unks([unk|List]) :- bads_or_unks(List).
+    
+% List contains exactly N bad items.
+nbads([], 0).
+nbads([bad|List], N) :- N > 0, Remain is N - 1, nbads(List, Remain).
+
+% read input file into [(good;bad;unk)]-[list of bad runs]
+input(FileName, Lines) :- phrase_from_file(lines(Lines), FileName).
+
+lines([]) --> eos.
+lines([Status-Parity|Lines]) --> status(Status), parity(Parity), lines(Lines).
+
+status([good]) --> " ".
+status([good|Cdr]) --> ".", status(Cdr).
+status([bad|Cdr]) --> "#", status(Cdr).
+status([unk|Cdr]) --> "?", status(Cdr).
+
+parity([N]) --> number(N), ("\n"; eos).
+parity([N|Cdr]) --> number(N), ",", parity(Cdr).

12/test.txt

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+???.### 1,1,3
+.??..??...?##. 1,1,3
+?#?#?#?#?#?#?#? 1,3,1,6
+????.#...#... 4,1,1
+????.######..#####. 1,6,5
+?###???????? 3,2,1