Day 4-2.

day4.erl

@@ -4,21 +4,26 @@
 
 solve(InputData) ->
 	Lines = binary:split(InputData, <<$\n>>, [trim_all, global]),
-	{part1(Lines), none}.
+	solver(Lines, {0, 0}).
 
-part1([]) -> 0;
-part1([Entry | Rest]) ->
+solver([], Acc) -> Acc;
+solver([Entry | Rest], {Part1, Part2}) ->
 	Ranges = binary:split(Entry, <<",">>, [trim_all, global]),
 	[[F1, F2], [S1, S2]] = lists:map(fun(Range) -> binary:split(Range, <<"-">>, [trim_all, global]) end, Ranges),
 	First = {binary_to_integer(F1), binary_to_integer(F2)},
 	Second = {binary_to_integer(S1), binary_to_integer(S2)},
-	io:format("~n~p ~p", [First, Second]),
-	case range_intersect(First, Second) of
-		First -> 1;
-		Second -> 1;
-		_SomethingElse -> io:format(" out"), 0
-	end + part1(Rest).
+	Intersection = range_intersect(First, Second),
+	{P1Flag, P2Flag} =
+	case Intersection of
+		First -> {1, 1};
+		Second -> {1, 1};
+		SomethingElse ->
+			case range_is_empty(Intersection) of
+				false -> {0, 1};
+				true -> {0, 0}
+			end
+	end,
+	solver(Rest, {Part1+P1Flag, Part2+P2Flag}).
 
-range_empty() -> {0, -1}.
 range_is_empty({Bottom, Top}) -> Top < Bottom.
 range_intersect({B1, T1}, {B2, T2}) -> {max(B1, B2), min(T1, T2)}.