2021/day4/day4.erl

   1 %% to compile: erlc day3A.erl
   2 %% to run: erl -noshell -s day3 solve
   3 %%
   4 -module(day4).
   5
   6 -export ([solve/0, solve/1, solve/2]).
   7 -export ([read_boards/0]).
   8
   9 solve() ->
  10     solve(['1']),
  11     solve(['2']),
  12     init:stop().
  13
  14 solve(A) ->
  15     solve(A, read_boards()).
  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_boards() ->
  27         {ok, IO} = file:open("boards.txt", 'read'),
  28         Data = read_boards(IO),
  29         file:close(IO),
  30         Data.
  31
  32 read_boards(IO) ->
  33         read_boards(IO, []).
  34
  35 read_boards('eof', Boards) ->
  36         Boards;
  37 read_boards(IO, Boards) ->
  38         case read_board(IO) of
  39                 'eof' -> Boards;
  40                 Board -> read_boards(IO, Boards ++ [Board])
  41         end.
  42
  43 read_board(IO) ->
  44         read_line(IO, []).
  45
  46 read_line(IO, Board) ->
  47         case file:read_line(IO) of
  48                 {ok, "\n"} -> make_board(Board);
  49                 'eof' -> 'eof';
  50                 {ok, Line} -> read_line(IO, [[ list_to_integer(X) || X <- string:tokens(Line, " \n")]|Board])
  51         end.
  52
  53 make_board(B) ->
  54         B ++ [lists:map(fun(X) -> lists:nth(Y,X) end, B) || Y <- lists:seq(1,5)].
  55
  56 solution1(Boards) ->
  57         Input = get_input(),
  58         Bingo = process(Boards, 1, Input),
  59         score(Bingo).
  60
  61 solution2(Boards) ->
  62         Input = get_input(),
  63         Bingo = process(Boards, length(Boards), Input),
  64         score(Bingo).
  65
  66 score({'bingo', Num, Board}) ->
  67         Fun = fun(L) -> lists:foldl(fun(X, Acc) -> X + Acc end, 0, L) end,
  68         Num * (Fun([Fun(X) || X <- Board]) / 2).
  69
  70 process(Boards, _Count, []) -> Boards;
  71 process(Boards, Count, [H|T]) ->
  72         New_boards = process_boards(Boards, H, []),
  73         case is_bingo(New_boards) of
  74                 {'bingo', Board} when Count ==  1 -> {'bingo', H, Board};
  75                 {'bingo', _Board}  ->
  76                         New_boards2 = delete_bingo_boards(New_boards),
  77                         process(New_boards2, Count - length(New_boards) + length(New_boards2), T);
  78                 _Else -> process(New_boards, Count, T)
  79         end.
  80
  81
  82 process_boards([], _Num, Acc) ->
  83         Acc;
  84 process_boards([B|T], Num, Acc) ->
  85         process_boards(T, Num, [[lists:delete(Num, X) || X <- B]|Acc]).
  86
  87 is_bingo([]) -> 'false';
  88 is_bingo([Board|Rest]) ->
  89         case is_line(Board) of
  90                 'true' -> {'bingo', Board};
  91                 'false' -> is_bingo(Rest)
  92         end.
  93 is_line(Board) ->
  94         lists:any(fun(X) -> X == [] end, Board).
  95
  96 delete_bingo_boards(Boards) ->
  97         [Board || Board <- Boards, not is_line(Board)].
  98
  99 get_input() ->
 100         [83,69,34,46,30,23,19,75,22,37,89,78,32,39,11,44,95,43,26,48,84,53,94,88,18,40,62,35,27,42,15,2,91,20,4,64,99,71,54,97,52,36,28,7,74,45,70,86,98,1,61,50,68,6,77,8,57,47,51,72,65,3,49,24,79,13,17,92,41,80,63,67,82,90,55,0,10,93,38,21,59,73,33,31,9,76,5,66,16,58,85,87,12,29,25,14,96,56,60,81].