day13/day13.erl

   1 %% to compile: erlc day3A.erl
   2 %% to run: erl -noshell -s day5 solve
   3 %%
   4 -module(day13).
   5
   6 -export ([solve/0, solve/1, solve/2]).
   7 -export ([read_input/0]).
   8
   9 solve() ->
  10     solve(['1']),
  11     solve(['2']),
  12     init:stop().
  13
  14 solve(A) ->
  15     solve(A, read_input()).
  16
  17 solve(['1'], D) ->
  18     io:format("The solution to ~p puzzle1 is: ~p~n", [?MODULE, solve(1, D)]);
  19 solve(1, D) ->
  20     solution1(D);
  21 solve(['2'], D) ->
  22     io:format("The solution to ~p puzzle2 is: ~p~n", [?MODULE, solve(2, D)]);
  23 solve(2, D) ->
  24     solution2(D).
  25
  26 read_input() ->
  27     {ok, IO} = file:open("input.txt", 'read'),
  28     Data = read_input(IO),
  29     file:close(IO),
  30     Data.
  31
  32 read_input(IO) ->
  33         read_input(IO, []).
  34
  35 read_input(IO, Input) ->
  36     case read_line(IO) of
  37         'eof' -> Input;
  38         Line -> read_input(IO, Input ++ [Line])
  39     end.
  40
  41 read_line(IO) ->
  42         case file:read_line(IO) of
  43                 'eof' -> 'eof';
  44                 {ok, Line} -> parse_line(Line)
  45         end.
  46
  47 parse_line(Line) ->
  48     Points = string:tokens(Line, " ,\n"),
  49     [X, Y] = [list_to_integer(X) || X <- Points],
  50     {X, Y}.
  51
  52 solution1(Input) ->
  53     io:format("Input ~p~n", [Input]),
  54     F1 = fold(x, 655, Input),
  55     length(F1).
  56
  57 solution2(Input) ->
  58     I = fold(y,6,fold(y,13,fold(y,27,fold(x,40,fold(y,55,fold(x,81,fold(y,111,fold(x,163,fold(y,223,fold(x,327,fold(y,447,fold(x,655, Input)))))))))))),
  59     MaxX = lists:foldl(fun({T, _}, Acc) -> case T > Acc of 'true' -> T; _ -> Acc end end, 0, I),
  60     MaxY = lists:foldl(fun({_, T}, Acc) -> case T > Acc of 'true' -> T; _ -> Acc end end, 0, I),
  61     Coords = [{X,Y} || Y <- lists:seq(0,MaxY), X <- lists:seq(0,MaxX)],
  62     output(Coords, I, MaxX).
  63
  64 output([], I, MaxX) -> ok;
  65 output([{X,Y}|Rest], I, MaxX) ->
  66         case lists:member({X,Y}, I) of
  67                 'true' -> io:format("#");
  68                 'false' -> io:format(" ")
  69         end,
  70         case X == MaxX of
  71                 'true' -> io:format("~n");
  72                 'false' -> ok
  73         end,
  74         output(Rest, I, MaxX).
  75
  76 fold(y, N, Input) ->
  77     L1 = [ {X, (Y * -1) + N}  || {X, Y} <- Input],
  78     {Sat, NotSat} = lists:partition(fun({_,Y}) -> Y < 0 end, L1),
  79     Sat2 = [{X, Y * -1}|| {X, Y} <- Sat],
  80     L2 = lists:usort(NotSat ++ Sat2),
  81     [ {X, (Y - N) * -1}  || {X,Y} <- L2];
  82 fold(x, N, Input) ->
  83     L1 = [ {(X * -1) + N, Y}  || {X, Y} <- Input],
  84     {Sat, NotSat} = lists:partition(fun({X,_}) -> X < 0 end, L1),
  85     Sat2 = [{X * -1, Y}|| {X, Y} <- Sat],
  86     L2 = lists:usort(NotSat ++ Sat2),
  87     [ {(X - N) * -1, Y}  || {X,Y} <- L2].
  88