From fe5a6959f9e01a19a6d5b8ee916462d5b7ee747f Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Mon, 7 Dec 2020 01:03:35 -0500
Subject: [PATCH] Add day 7 part 1 soln

---
 day7/Makefile |  15 ++++++
 day7/day7.cpp | 144 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 159 insertions(+)
 create mode 100644 day7/Makefile
 create mode 100644 day7/day7.cpp

diff --git a/day7/Makefile b/day7/Makefile
new file mode 100644
index 0000000..9acfc18
--- /dev/null
+++ b/day7/Makefile
@@ -0,0 +1,15 @@
+CC=g++
+BIN_NAME=day7
+CCFLAGS=-o $(BIN_NAME) -g -std=c++17
+LDFLAGS=-lfolly
+
+.PHONY: all, clean
+
+all: $(BIN_NAME)
+
+clean:
+	rm -f $(BIN_NAME)
+
+$(BIN_NAME): day7.cpp
+	$(CC) $(CCFLAGS) $(LDFLAGS) day7.cpp
+
diff --git a/day7/day7.cpp b/day7/day7.cpp
new file mode 100644
index 0000000..a04e2a0
--- /dev/null
+++ b/day7/day7.cpp
@@ -0,0 +1,144 @@
+#include <folly/String.h>
+
+#include <algorithm>
+#include <execution>
+#include <fstream>
+#include <iostream>
+#include <map>
+#include <numeric>
+#include <regex>
+#include <set>
+#include <string_view>
+#include <vector>
+
+auto constexpr LINE_PATTERN = R"((.*) bags? contain (.*)\.)";
+auto constexpr BAG_PATTERN = R"((\d) (.*) bags?)";
+auto constexpr NO_OTHER_BAGS = "no other bags";
+auto constexpr BAG_DELIM = ", ";
+auto constexpr DESIRED_BAG = "shiny gold";
+
+class ContainedBag {
+ public:
+	ContainedBag(std::string color, int quantity) : color(color), quantity(quantity) {
+	}
+
+	const std::string &getColor() const {
+		return this->color;
+	}
+
+	int getQuantity() const {
+		return this->quantity;
+	}
+
+	bool operator==(ContainedBag bag) {
+		return bag.getColor() == this->getColor() && bag.getQuantity() == this->getQuantity();
+	}
+
+ private:
+	std::string color;
+	int quantity;
+};
+
+// I would use a set for the value but I don't want to deal with hash functions right now
+using BagMap = std::map<std::string, std::vector<ContainedBag>>;
+
+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::pair<std::string, std::vector<ContainedBag>> parseInputLine(const std::string &line) {
+	std::regex lineExpression(LINE_PATTERN);
+	std::smatch lineMatches;
+	if (!std::regex_match(line, lineMatches, lineExpression)) {
+		throw new std::invalid_argument("Invalid input line");
+	}
+
+	std::string bagName = lineMatches[1];
+	std::string allUnparsedBags = lineMatches[2];
+	std::vector<std::string> unparsedBags;
+	folly::split(BAG_DELIM, allUnparsedBags, unparsedBags);
+	std::vector<ContainedBag> containedBags;
+	for (const std::string &unparsedBag : unparsedBags) {
+		// Check for no bags contained
+		if (unparsedBag == NO_OTHER_BAGS) {
+			continue;
+		}
+
+		// Check for some quantity of bags contained
+		std::regex bagExpression(BAG_PATTERN);
+		std::smatch bagMatches;
+		if (!std::regex_match(unparsedBag, bagMatches, bagExpression)) {
+			throw new std::invalid_argument("Invalid bagspec");
+		}
+
+		ContainedBag containedBag(bagMatches[2], std::stoi(bagMatches[1]));
+		containedBags.push_back(containedBag);
+	}
+
+	return std::pair<std::string, std::vector<ContainedBag>>(bagName, containedBags);
+}
+
+BagMap makeBagMap(const std::vector<std::string> &input) {
+	std::map<std::string, std::vector<ContainedBag>> bags;
+	std::transform(input.cbegin(), input.cend(), std::inserter(bags, bags.begin()), [](const std::string &line) {
+		return parseInputLine(line);
+	});
+
+	return bags;
+}
+
+bool doesBagContain(BagMap bagMap, const std::string &originBag, const std::string &desiredBag) {
+	std::stack<std::string> toVisit;
+	std::set<std::string> visited;
+	toVisit.emplace(originBag);
+	while (!toVisit.empty()) {
+		std::string visiting = toVisit.top();
+		toVisit.pop();
+		if (visited.find(visiting) != visited.end()) {
+			continue;
+		}
+
+		if (visiting == desiredBag) {
+			return true;
+		}
+
+		for (ContainedBag bag : bagMap.at(visiting)) {
+			toVisit.emplace(std::string(bag.getColor()));
+		}
+	}
+
+	return false;
+}
+
+int part1(const std::vector<std::string> &input) {
+	auto bagMap = makeBagMap(input);
+	int count = 0;
+	for (auto bagEntry : bagMap) {
+		const std::string &bagName = bagEntry.first;
+		if (bagName == DESIRED_BAG) {
+			continue;
+		}
+
+		count += doesBagContain(bagMap, bagName, DESIRED_BAG);
+	}
+
+	return count;
+}
+
+int main(int argc, char *argv[]) {
+	if (argc != 2) {
+		std::cerr << argv[0] << " <input_file>" << std::endl;
+		return 1;
+	}
+
+	auto input = readInput(argv[1]);
+	std::cout << part1(input) << std::endl;
+	// std::cout << part2(groups) << std::endl;
+}