From 76f683ee8c2ce043e1f480373d30819551b6dce5 Mon Sep 17 00:00:00 2001
From: Nick Krichevsky <nick@ollien.com>
Date: Sat, 26 Dec 2020 02:09:41 -0500
Subject: [PATCH] Add day 23 part 1

---
 day23/Makefile  |  15 ++++++
 day23/day23.cpp | 123 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 138 insertions(+)
 create mode 100644 day23/Makefile
 create mode 100644 day23/day23.cpp

diff --git a/day23/Makefile b/day23/Makefile
new file mode 100644
index 0000000..9fefeaa
--- /dev/null
+++ b/day23/Makefile
@@ -0,0 +1,15 @@
+CC=g++
+BIN_NAME=day23
+CCFLAGS=-o $(BIN_NAME) -g -std=c++17
+LDFLAGS=
+
+.PHONY: all, clean
+
+all: $(BIN_NAME)
+
+clean:
+	rm -f $(BIN_NAME)
+
+$(BIN_NAME): day23.cpp
+	$(CC) $(CCFLAGS) $(LDFLAGS) day23.cpp
+
diff --git a/day23/day23.cpp b/day23/day23.cpp
new file mode 100644
index 0000000..3b7066c
--- /dev/null
+++ b/day23/day23.cpp
@@ -0,0 +1,123 @@
+#include <boost/hana/any_of.hpp>
+#include <boost/hana/ext/std/tuple.hpp>
+#include <boost/hana/for_each.hpp>
+#include <fstream>
+#include <functional>
+#include <iostream>
+#include <list>
+#include <numeric>
+#include <string>
+#include <tuple>
+
+constexpr int NUM_CRAB_TURNS = 100;
+
+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<int> makeCupList(const std::string &inputLine) {
+	std::vector<int> cups;
+	std::transform(inputLine.cbegin(), inputLine.cend(), std::back_inserter(cups), [](char rawNum) {
+		if (rawNum < '0' || rawNum > '9') {
+			throw std::invalid_argument("Not numeric");
+		}
+
+		return rawNum - '0';
+	});
+
+	return cups;
+}
+
+std::tuple<int, int, int> getPickedUpCups(int currentCupIndex, const std::vector<int> &cupList) {
+	return std::make_tuple(
+		cupList.at((currentCupIndex + 1) % cupList.size()),
+		cupList.at((currentCupIndex + 2) % cupList.size()),
+		cupList.at((currentCupIndex + 3) % cupList.size()));
+}
+
+template <typename Tuple, typename ValueType>
+bool tupleContainsItem(Tuple tuple, ValueType value) {
+	return boost::hana::any_of(tuple, [value](ValueType item) { return item == value; });
+}
+
+int findDestinationCup(int currentCupIndex, const std::vector<int> &cupList) {
+	int currentCup = cupList.at(currentCupIndex);
+	std::tuple<int, int, int> pickedUpCups = getPickedUpCups(currentCupIndex, cupList);
+	auto cupMinMaxIterators = std::minmax_element(cupList.cbegin(), cupList.cend());
+	std::pair<int, int> cupMinMax = std::make_pair(*(cupMinMaxIterators.first), *(cupMinMaxIterators.second));
+
+	int destinationCup = currentCup;
+	do {
+		destinationCup--;
+		if (destinationCup < cupMinMax.first) {
+			destinationCup = cupMinMax.second;
+		}
+	} while (tupleContainsItem(pickedUpCups, destinationCup));
+
+	return destinationCup;
+}
+
+std::string makeFullCupLabel(const std::vector<int> cups) {
+	std::string output;
+	output.reserve(cups.size() - 1);
+	auto startIt = std::find(cups.cbegin(), cups.cend(), 1);
+	for (int i = (startIt - cups.begin() + 1) % cups.size(); cups.at(i) != 1; i = (i + 1) % cups.size()) {
+		output.push_back(cups.at(i) + '0');
+	}
+
+	return output;
+}
+
+std::string part1(const std::string &inputLine) {
+	std::vector<int> cups = makeCupList(inputLine);
+	int currentCup = cups.front();
+	for (int i = 0; i < NUM_CRAB_TURNS; i++) {
+		auto currentCupIt = std::find(cups.cbegin(), cups.cend(), currentCup);
+		int destinationCup = findDestinationCup(currentCupIt - cups.cbegin(), cups);
+		std::tuple<int, int, int> pickedUpCups = getPickedUpCups(currentCupIt - cups.cbegin(), cups);
+
+		// Perform the cup moves
+		std::vector<int> newCups;
+		newCups.reserve(cups.size());
+		for (int cup : cups) {
+			if (tupleContainsItem(pickedUpCups, cup)) {
+				continue;
+			}
+
+			newCups.push_back(cup);
+			// Copy the existing cups over
+			if (cup == destinationCup) {
+				boost::hana::for_each(pickedUpCups, [&newCups](int item) { newCups.push_back(item); });
+			}
+		}
+
+		// Get the new current cup
+		cups = std::move(newCups);
+		currentCupIt = std::find(cups.cbegin(), cups.cend(), currentCup);
+		if (currentCupIt + 1 == cups.cend()) {
+			currentCup = cups.front();
+		} else {
+			currentCup = *(currentCupIt + 1);
+		}
+	}
+
+	return makeFullCupLabel(cups);
+}
+
+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.at(0)) << std::endl;
+}