Add part 1 solution

day12/day12.cpp

@@ -0,0 +1,138 @@
+#include <algorithm>
+#include <charconv>
+#include <fstream>
+#include <iostream>
+#include <numeric>
+#include <optional>
+#include <vector>
+
+constexpr int NUM_DIRECTIONS = 4;
+enum CardinalDirection { NORTH = 0, EAST = 1, SOUTH = 2, WEST = 3 };
+
+class Ship {
+ public:
+	Ship(CardinalDirection direction, std::pair<int, int> position) : direction(direction), position(position) {
+	}
+
+	const std::pair<int, int> &getPosition() const {
+		return this->position;
+	}
+
+	CardinalDirection getDirection() const {
+		return direction;
+	}
+
+	void setDirection(CardinalDirection direction) {
+		this->direction = direction;
+	}
+
+	void move(int value) {
+		this->move(value, this->direction);
+	}
+
+	void move(int value, CardinalDirection direction) {
+		int delta = (direction == SOUTH || direction == EAST) ? -value : value;
+		if (direction == NORTH || direction == SOUTH) {
+			this->position.second += delta;
+		} else {
+			this->position.first += delta;
+		}
+	}
+
+	void turnLeft(int deg) {
+		this->addToDirection(3 * deg / 90);
+	}
+
+	void turnRight(int deg) {
+		// Three lefts make a right - easier than dealing with negative mods
+		this->addToDirection(deg / 90);
+	}
+
+ private:
+	void addToDirection(int delta) {
+		this->direction = static_cast<CardinalDirection>((this->direction + delta) % NUM_DIRECTIONS);
+	}
+
+	CardinalDirection direction;
+	std::pair<int, int> position;
+};
+
+std::vector<std::string> readInput(const std::string &filename) {
+	std::vector<std::string> input;
+	std::string line;
+	std::ifstream file(filename);
+	while (std::getline(file, line)) {
+		input.push_back(line);
+	}
+
+	return input;
+}
+
+std::vector<std::pair<char, int>> parseInput(const std::vector<std::string> &input) {
+	std::vector<std::pair<char, int>> parsedInput;
+	parsedInput.reserve(input.size());
+	for (std::string_view line : input) {
+		char direction = line.at(0);
+		auto rawMagnitude = line.substr(1);
+		int magnitude;
+		auto parseResult = std::from_chars(rawMagnitude.data(), rawMagnitude.data() + rawMagnitude.size(), magnitude);
+		if (parseResult.ec == std::errc::invalid_argument) {
+			throw std::invalid_argument("Invalid input");
+		}
+
+		parsedInput.push_back(std::pair<char, int>(direction, magnitude));
+	}
+
+	return parsedInput;
+}
+
+void makeMove(Ship &ship, const std::pair<char, int> &move) {
+	char directive = move.first;
+	int magnitude = move.second;
+	switch (directive) {
+		case 'L':
+			ship.turnLeft(magnitude);
+			break;
+		case 'R':
+			ship.turnRight(magnitude);
+			break;
+		case 'N':
+			ship.move(magnitude, NORTH);
+			break;
+		case 'S':
+			ship.move(magnitude, SOUTH);
+			break;
+		case 'E':
+			ship.move(magnitude, EAST);
+			break;
+		case 'W':
+			ship.move(magnitude, WEST);
+			break;
+		case 'F':
+			ship.move(magnitude);
+			break;
+		default:
+			throw std::invalid_argument("Invalid move direction");
+	}
+}
+
+int part1(const std::vector<std::pair<char, int>> &input) {
+	Ship ship(EAST, std::pair<int, int>(0, 0));
+	for (auto &move : input) {
+		makeMove(ship, move);
+	}
+
+	return abs(ship.getPosition().first) + abs(ship.getPosition().second);
+}
+
+int main(int argc, char *argv[]) {
+	if (argc != 2) {
+		std::cerr << argv[0] << " <input_file>" << std::endl;
+		return 1;
+	}
+
+	auto input = readInput(argv[1]);
+	auto parsedInput = parseInput(input);
+
+	std::cout << part1(parsedInput) << std::endl;
+}