Add day 24 part 1

day24/Makefile

@@ -0,0 +1,15 @@
+CC=g++
+BIN_NAME=day24
+CCFLAGS=-o $(BIN_NAME) -g -O2 -std=c++17
+LDFLAGS=
+
+.PHONY: all, clean
+
+all: $(BIN_NAME)
+
+clean:
+	rm -f $(BIN_NAME)
+
+$(BIN_NAME): day24.cpp
+	$(CC) $(CCFLAGS) $(LDFLAGS) day24.cpp
+

day24/day24.cpp

@@ -0,0 +1,91 @@
+#include <fstream>
+#include <functional>
+#include <iostream>
+#include <numeric>
+#include <regex>
+#include <string>
+#include <tuple>
+
+enum Direction { EAST, WEST, SOUTH_EAST, SOUTH_WEST, NORTH_WEST, NORTH_EAST };
+
+constexpr auto DIRECTION_PATTERN = R"(e|w|se|sw|nw|ne)";
+const std::map<std::string, Direction> INPUT_TO_DIRECTION{
+	std::make_pair("e", EAST),
+	std::make_pair("w", WEST),
+	std::make_pair("se", SOUTH_EAST),
+	std::make_pair("sw", SOUTH_WEST),
+	std::make_pair("nw", NORTH_WEST),
+	std::make_pair("ne", NORTH_EAST),
+};
+
+const std::map<Direction, std::pair<int, int>> DIRECTION_TO_DELTA{
+	std::make_pair(EAST, std::make_pair(-2, 0)),
+	std::make_pair(WEST, std::make_pair(2, 0)),
+	std::make_pair(SOUTH_EAST, std::make_pair(-1, -1)),
+	std::make_pair(SOUTH_WEST, std::make_pair(1, -1)),
+	std::make_pair(NORTH_WEST, std::make_pair(1, 1)),
+	std::make_pair(NORTH_EAST, std::make_pair(-1, 1)),
+};
+
+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<Direction> parseInputLine(const std::string &inputLine) {
+	std::regex directionPattern(DIRECTION_PATTERN);
+	std::vector<Direction> res;
+	std::transform(
+		std::sregex_iterator(inputLine.cbegin(), inputLine.cend(), directionPattern),
+		std::sregex_iterator(),
+		std::back_inserter(res),
+		[](const std::smatch &match) {
+			std::string directionStr = match.str();
+			return INPUT_TO_DIRECTION.at(directionStr);
+		});
+
+	return res;
+}
+
+std::vector<std::vector<Direction>> parseInput(const std::vector<std::string> &input) {
+	std::vector<std::vector<Direction>> res;
+	std::transform(input.cbegin(), input.cend(), std::back_inserter(res), parseInputLine);
+
+	return res;
+}
+
+template <typename Iter>
+std::pair<int, int> getPosition(Iter start, Iter end) {
+	return std::accumulate(start, end, std::make_pair(0, 0), [](std::pair<int, int> position, const Direction &dir) {
+		std::pair<int, int> delta = DIRECTION_TO_DELTA.at(dir);
+		return std::make_pair(position.first + delta.first, position.second + delta.second);
+	});
+}
+
+int part1(const std::vector<std::vector<Direction>> &input) {
+	std::map<std::pair<int, int>, bool> flipped;
+	for (const std::vector<Direction> &sequence : input) {
+		std::pair<int, int> pos = getPosition(sequence.cbegin(), sequence.cend());
+		flipped[pos] = !flipped[pos];
+	}
+
+	return std::count_if(flipped.cbegin(), flipped.cend(), [](auto entry) { return entry.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;
+}