Clean up day 16

day16/day16.cpp

@@ -11,12 +11,16 @@
 
 constexpr auto NEARBY_TICKETS_HEADER = "nearby tickets:";
 constexpr auto YOUR_TICKET_HEADER = "your ticket:";
+constexpr auto DEPARTURE_PREFIX = "departure";
 constexpr auto FIELD_PATTERN = R"((.*): (\d+)-(\d+) or (\d+)-(\d+))";
 
 // This has to be the grossest type signature I've written in a while, but it's of
 // a-b or c-d maps to pair<a, b> or pair<c ,d>
 using RangeSpec = std::pair<std::pair<int, int>, std::pair<int, int>>;
 
+/**
+ * A field of the ticket
+ */
 class TicketField {
  public:
 	TicketField(std::string &name, RangeSpec &ranges) : name(name), ranges(ranges) {
@@ -47,6 +51,9 @@ class TicketField {
 	RangeSpec ranges;
 };
 
+/**
+ * The specification of all tickets from the puzzle input
+ */
 class TicketSpec {
  public:
 	TicketSpec(
@@ -88,6 +95,13 @@ std::vector<std::string> readInput(const std::string &filename) {
 	return input;
 }
 
+/**
+ * Parse the fields of the ticket specification
+ * @tparam Iter The type of iterator to get the fields from
+ * @param start The start iterator
+ * @param end The end iterator
+ * @return std::vector<TicketField> All of the ticket fields from the input
+ */
 template <typename Iter>
 std::vector<TicketField> parseFields(Iter start, Iter end) {
 	std::vector<TicketField> fields;
@@ -106,6 +120,11 @@ std::vector<TicketField> parseFields(Iter start, Iter end) {
 	return fields;
 }
 
+/**
+ * Parse a single ticket
+ * @param rawTicket The ticket to parse
+ * @return std::vector<int> The ticket's fields
+ */
 std::vector<int> parseTicket(const std::string &rawTicket) {
 	std::vector<int> ticket;
 	folly::split(",", rawTicket, ticket);
@@ -113,6 +132,13 @@ std::vector<int> parseTicket(const std::string &rawTicket) {
 	return ticket;
 }
 
+/**
+ * Get all of the nearby tickets
+ * @tparam Iter The iterator type to get the nearby tickets
+ * @param start The start iterator
+ * @param end The end iterator
+ * @return std::vector<std::vector<int>> The nearby tickets and their fields
+ */
 template <typename Iter>
 std::vector<std::vector<int>> parseNearbyTickets(Iter start, Iter end) {
 	std::vector<std::vector<int>> nearbyTickets;
@@ -124,6 +150,11 @@ std::vector<std::vector<int>> parseNearbyTickets(Iter start, Iter end) {
 	return nearbyTickets;
 }
 
+/**
+ * Parse the puzzle input
+ * @param input The puzzle input
+ * @return TicketSpec The puzzle input as a TicketSpec
+ */
 TicketSpec parseInput(const std::vector<std::string> &input) {
 	auto fieldsEnd = std::find(input.cbegin(), input.cend(), "");
 	auto yourTicketBegin = std::find(input.cbegin(), input.cend(), YOUR_TICKET_HEADER);
@@ -134,6 +165,14 @@ TicketSpec parseInput(const std::vector<std::string> &input) {
 
 	return TicketSpec(std::move(yourTicket), std::move(nearbyTickets), std::move(pairs));
 }
+
+/**
+ * Checks if a value is in range for all of the ticket's ranges
+ * @param value THe value to check
+ * @param ticketSpec The ticket specification to check against
+ * @return true If the value is valid
+ * @return false If the value is nto valid
+ */
 bool inRangesForTicket(int value, const TicketSpec &ticketSpec) {
 	return std::any_of(
 		ticketSpec.getFields().cbegin(), ticketSpec.getFields().cend(), [value](const TicketField &field) {
@@ -141,6 +180,11 @@ bool inRangesForTicket(int value, const TicketSpec &ticketSpec) {
 		});
 }
 
+/**
+ * Get all of the valid tickets in the input
+ * @param ticketSpec The ticket spec from the input
+ * @return std::vector<std::vector<int>> The valid tickets
+ */
 std::vector<std::vector<int>> getValidTickets(const TicketSpec &ticketSpec) {
 	// There might be a nicer way than copying these but frankly I can't think of one that's clean.
 	std::vector<std::vector<int>> allTickets(ticketSpec.getOtherTickets());
@@ -159,19 +203,12 @@ std::vector<std::vector<int>> getValidTickets(const TicketSpec &ticketSpec) {
 	return allTickets;
 }
 
-int part1(const TicketSpec &ticketSpec) {
+/**
-	return std::accumulate(
+ * Generate candidates of what fields could possibly be used for each position in the tickets
-		ticketSpec.getOtherTickets().cbegin(),
+ * @param ticketSpec The ticket specification from the problem
-		ticketSpec.getOtherTickets().cend(),
+ * @return std::map<TicketField, std::set<int>> A map of the field candidates
-		0,
+ */
-		[&ticketSpec](int total, const std::vector<int> &ticket) {
+std::map<TicketField, std::set<int>> generateFieldCandidates(const TicketSpec &ticketSpec) {
-			return total + std::accumulate(ticket.cbegin(), ticket.cend(), 0, [&ticketSpec](int subtotal, int field) {
-					   return inRangesForTicket(field, ticketSpec) ? subtotal : subtotal + field;
-				   });
-		});
-}
-
-long part2(const TicketSpec &ticketSpec) {
 	auto validTickets = getValidTickets(ticketSpec);
 	std::map<TicketField, std::set<int>> fieldCandidates;
 	for (const TicketField &field : ticketSpec.getFields()) {
@@ -186,6 +223,16 @@ long part2(const TicketSpec &ticketSpec) {
 		}
 	}
 
+	return fieldCandidates;
+}
+
+/**
+ * Determine which fields map to what positions in the tickets
+ * @param ticketSpec The ticket specification from the input
+ * @return std::map<TicketField, int> A mapping of fields to positions in the tickets
+ */
+std::map<TicketField, int> determineFieldPositions(const TicketSpec &ticketSpec) {
+	std::map<TicketField, std::set<int>> fieldCandidates = generateFieldCandidates(ticketSpec);
 	std::map<TicketField, int> fieldPositions;
 	for (auto candidate : fieldCandidates) {
 		std::set<int> valid = candidate.second;
@@ -206,20 +253,41 @@ long part2(const TicketSpec &ticketSpec) {
 				valid = std::move(difference);
 			}
 		}
-		assert(valid.size() == 1);
+		if (valid.size() != 1) {
+			throw new std::invalid_argument("Invalid input; not possible to determine the field mappings.");
+		}
+
 		fieldPositions.emplace(candidate.first, *valid.begin());
 	}
-	long total = 1;
+
-	for (const auto &fieldPosition : fieldPositions) {
+	return fieldPositions;
+}
+
+int part1(const TicketSpec &ticketSpec) {
+	return std::accumulate(
+		ticketSpec.getOtherTickets().cbegin(),
+		ticketSpec.getOtherTickets().cend(),
+		0,
+		[&ticketSpec](int total, const std::vector<int> &ticket) {
+			return total + std::accumulate(ticket.cbegin(), ticket.cend(), 0, [&ticketSpec](int subtotal, int field) {
+					   return inRangesForTicket(field, ticketSpec) ? subtotal : subtotal + field;
+				   });
+		});
+}
+
+long part2(const TicketSpec &ticketSpec) {
+	auto fieldPositions = determineFieldPositions(ticketSpec);
+	return std::accumulate(
+		fieldPositions.cbegin(),
+		fieldPositions.cend(),
+		1L,
+		[&ticketSpec](long total, std::pair<TicketField, int> fieldPosition) {
 			auto fieldName = fieldPosition.first.getName();
-		if (fieldName.rfind("departure", 0) != 0) {
+			if (fieldName.rfind(DEPARTURE_PREFIX, 0) != 0) {
-			continue;
-		}
-
-		total *= ticketSpec.getOurTicket().at(fieldPosition.second);
-	}
-
 				return total;
+			}
+			return total * ticketSpec.getOurTicket().at(fieldPosition.second);
+		});
 }
 
 int main(int argc, char *argv[]) {