d14p2 for real

14/part2.pl

@@ -4,14 +4,45 @@
 
 main([FileName|_]) :-
     input(FileName, Input),
-    concurrent_maplist(row_weight, Rocks, Weights),
-    sum_list(Weights, W),
-    writef('%t\n', [W]).
+    rolls(Input, 0, [], First-Cycle-Hist),
+    reverse(Hist, [_|TrueHist]),
+    BillionOffset is ((999999999 - First) mod Cycle) + First,
+    nth0(BillionOffset, TrueHist, BillionMap),
+    % maplist({TrueHist}/[M]>>(
+    %     nth0(Nth, TrueHist, M),
+    %     map_weight(M, W),
+    %     writef('Weight(%t) = %t\n', [Nth, W]),
+    %     print(M)), TrueHist),
+    write('======================\n'),
+    print(BillionMap),
+    map_weight(BillionMap, FinalWeight),
+    writef('First = %t, Cycle = %t, FinalOffset = %t, Answer = %t\n',
+           [First, Cycle, BillionOffset, FinalWeight]).
 
-row_weight(Row, Weight) :-
-    phrase(rock_counts(Rocks), Row),
-    convlist([N-z-_, N]>>(true), Rocks, RockCounts),
-    sum_list(RockCounts, Weight).
+map_weight(Map, W) :- rotate(Map, Rotated), map_weight(Rotated, _, W).
+
+map_weight([_], 0, 0).
+map_weight([Row|Map], RowI, W) :-
+    map_weight(Map, PrevRowI, PrevW),
+    RowI is PrevRowI + 1,
+    include(['O']>>(true), Row, Rocks),
+    length(Rocks, NRocks),
+    W is PrevW + RowI*NRocks.
+
+rolls(Map, N, Hist, First-Cycle-Hist) :-
+    match(Map, Hist, Cycle),
+    First is N - Cycle - 1,
+    !.
+rolls(Map, N, Hist, X) :-
+    roll(Map, NewMap),
+    NextN is N + 1,
+    NewHist = [Map|Hist],
+    rolls(NewMap, NextN, NewHist, X).
+
+match(Map, [Map|_], 1) :- !.
+match(Map, [_|Entries], N) :-
+    match(Map, Entries, NextN),
+    N is NextN + 1.
 
 % North is to the left
 roll(Map, NewMap) :-
@@ -38,12 +69,9 @@ print(Map) :-
     write('\n').
 
 collapse(Row, NewRow) :-
-    % abolish_private_tables,
-    % table(rock_counts/3), table(condense/3), table(reexpand/3),
     phrase(rock_counts(Counts), Row),
     phrase(condense(Zs), Counts),
     phrase(reexpand(Zs), NewRow),
-    % NewRow = Zs,
     true.
 
 reexpand([]) --> eos.