102 lines
2.3 KiB
Erlang
102 lines
2.3 KiB
Erlang
%% to compile: erlc day3A.erl
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%% to run: erl -noshell -s day3 solve
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%%
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-module(day10).
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-export ([solve/0, solve/1, solve/2]).
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-export ([read_input/0]).
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solve() ->
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solve(['1']),
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solve(['2']),
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init:stop().
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solve(A) ->
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solve(A, read_input()).
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solve(['1'], D) ->
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io:format("The solution to ~p puzzle1 is: ~p~n", [?MODULE, solve(1, D)]);
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solve(1, D) ->
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solution1(D);
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solve(['2'], D) ->
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io:format("The solution to ~p puzzle2 is: ~p~n", [?MODULE, solve(2, D)]);
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solve(2, D) ->
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solution2(D).
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read_input() ->
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{ok, IO} = file:open("input.txt", 'read'),
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Data = read_input(IO),
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file:close(IO),
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Data.
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read_input(IO) ->
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read_input(IO, []).
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read_input(IO, Input) ->
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case read_line(IO) of
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'eof' -> Input;
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Line -> read_input(IO, Input ++ [Line])
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end.
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read_line(IO) ->
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case file:read_line(IO) of
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'eof' -> 'eof';
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{ok, Line} -> [ X || X <- Line, [X] /= "\n"]
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end.
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solution1(Input) ->
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lists:sum([parse(X) || X <- Input]).
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solution2(Input) ->
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List = [incomplete(X) || X <- Input],
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Filter_fail = lists:filter(fun(X) -> X /= 'failed' end, List),
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Scores = lists:sort([lists:foldl(fun(X, Acc) -> (Acc * 5) + value(X) end, 0, F) || F <- Filter_fail]),
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lists:nth(length(Scores) div 2 + 1, Scores).
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incomplete([H|T] = Input) ->
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io:format("~p~n", [Input]),
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try
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incomplete(T, [partner(H)])
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of
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ok -> 'ok';
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{incomplete, Rest} -> Rest
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catch
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_:_ -> 'failed'
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end.
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incomplete([], Expected) -> {incomplete, Expected};
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incomplete(Rest, []) -> {incomplete, incomplete(Rest)};
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incomplete([H|T], [H|Rest]) -> incomplete(T, Rest);
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incomplete([H|T], Expected) -> incomplete(T, [partner(H)|Expected]).
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parse([H|T] = Input) ->
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io:format("~p~n", [Input]),
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try
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parse(T, [partner(H)])
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of
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_ -> 0
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catch
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_:{invalid_partner,")"} -> 3;
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_:{invalid_partner,"]"} -> 57;
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_:{invalid_partner,"}"} -> 1197;
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_:{invalid_partner,">"} -> 25137
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end.
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parse([], Expected) -> {parsed, Expected};
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parse(Rest, []) -> {incomplete, parse(Rest)};
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parse([H|T], [H|Rest]) -> parse(T, Rest);
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parse([H|T], Expected) -> parse(T, [partner(H)|Expected]).
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partner($() -> $);
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partner($[) -> $];
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partner(${) -> $};
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partner($<) -> $>;
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partner(X) -> throw({invalid_partner, [X]}).
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value($)) -> 1;
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value($]) -> 2;
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value($}) -> 3;
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value($>) -> 4.
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