alan day10 erlang

day10/day10.erl

@@ -0,0 +1,101 @@
+%% to compile: erlc day3A.erl
+%% to run: erl -noshell -s day3 solve
+%%
+-module(day10).
+
+-export ([solve/0, solve/1, solve/2]).
+-export ([read_input/0]).
+
+solve() ->
+    solve(['1']),
+    solve(['2']),
+    init:stop().
+
+solve(A) ->
+    solve(A, read_input()).
+
+solve(['1'], D) ->
+    io:format("The solution to ~p puzzle1 is: ~p~n", [?MODULE, solve(1, D)]);
+solve(1, D) ->
+    solution1(D);
+solve(['2'], D) ->
+    io:format("The solution to ~p puzzle2 is: ~p~n", [?MODULE, solve(2, D)]);
+solve(2, D) ->
+    solution2(D).
+
+read_input() ->
+	{ok, IO} = file:open("input.txt", 'read'),
+	Data = read_input(IO),
+	file:close(IO),
+        Data.
+
+read_input(IO) ->
+	read_input(IO, []).
+
+read_input(IO, Input) ->
+	case read_line(IO) of
+		'eof' -> Input;
+		Line -> read_input(IO, Input ++ [Line])
+	end.
+
+read_line(IO) ->
+	case file:read_line(IO) of
+		'eof' -> 'eof';
+		{ok, Line} -> [ X || X <- Line, [X] /= "\n"]
+	end.
+
+solution1(Input) ->
+    lists:sum([parse(X) || X <- Input]).
+
+solution2(Input) ->
+    List = [incomplete(X) || X <- Input],
+    Filter_fail = lists:filter(fun(X) -> X /= 'failed' end, List),
+    Scores = lists:sort([lists:foldl(fun(X, Acc) -> (Acc * 5) + value(X) end, 0, F) || F <- Filter_fail]),
+    lists:nth(length(Scores) div 2 + 1, Scores).
+
+incomplete([H|T] = Input) ->
+    io:format("~p~n", [Input]),
+    try
+        incomplete(T, [partner(H)])
+    of
+	ok -> 'ok';
+	{incomplete, Rest} -> Rest
+    catch
+        _:_ -> 'failed' 
+    end.
+
+incomplete([], Expected) -> {incomplete, Expected};
+incomplete(Rest, []) ->  {incomplete, incomplete(Rest)};
+
+incomplete([H|T], [H|Rest]) -> incomplete(T, Rest);
+incomplete([H|T], Expected) -> incomplete(T, [partner(H)|Expected]).
+
+parse([H|T] = Input) ->
+    io:format("~p~n", [Input]),
+    try
+        parse(T, [partner(H)])
+    of
+	_ -> 0
+    catch
+        _:{invalid_partner,")"} -> 3;
+        _:{invalid_partner,"]"} -> 57;
+        _:{invalid_partner,"}"} -> 1197;
+        _:{invalid_partner,">"} -> 25137
+    end.
+
+parse([], Expected) -> {parsed, Expected};
+parse(Rest, []) ->  {incomplete, parse(Rest)};
+
+parse([H|T], [H|Rest]) -> parse(T, Rest);
+parse([H|T], Expected) -> parse(T, [partner(H)|Expected]).
+
+partner($() -> $);
+partner($[) -> $];
+partner(${) -> $};
+partner($<) -> $>;
+partner(X) -> throw({invalid_partner, [X]}).
+
+value($)) -> 1;
+value($]) -> 2;
+value($}) -> 3;
+value($>) -> 4.