From 002d023c65570ab88f36622a71a8c7c74a3c6309 Mon Sep 17 00:00:00 2001
From: Benjamin Kraft <benjamin.kraft@online.de>
Date: Tue, 13 Dec 2022 14:05:48 +0100
Subject: [PATCH] Day13 (I love to over-engineer things)

---
 src/days/13/Day13.cpp | 133 +++++++++++++++++++++++++++++++++++++++++-
 src/days/13/Day13.h   |  24 ++++++++
 2 files changed, 154 insertions(+), 3 deletions(-)

diff --git a/src/days/13/Day13.cpp b/src/days/13/Day13.cpp
index 6fd9442..247c0d8 100644
--- a/src/days/13/Day13.cpp
+++ b/src/days/13/Day13.cpp
@@ -1,9 +1,136 @@
 #include "Day13.h"
 
 Result Day13::Task1() {
-	return Day::Task1();
+
+	auto pairs = parsePacketPairs();
+	uint64 sum = 0;
+	for (size_t i = 0; i < pairs.size(); i++){
+		PacketPair p = pairs[i];
+
+		if (p.first->compare(p.second) == LOWER)
+			sum += i + 1;
+
+		delete p.first;
+		delete p.second;
+	}
+
+	return to_string(sum);
 }
 
 Result Day13::Task2() {
-	return Day::Task2();
-}
\ No newline at end of file
+	auto pairs = parsePacketPairs();
+	vector<Packet*> packets;
+	for (const auto &p : pairs){
+		packets.push_back(p.first);
+		packets.push_back(p.second);
+	}
+
+	Packet* firstAdd = Packet::parse("[[2]]");
+	Packet* secondAdd = Packet::parse("[[6]]");
+	packets.push_back(firstAdd);
+	packets.push_back(secondAdd);
+
+	std::sort(packets.begin(), packets.end(), [](Packet* p1, Packet* p2){
+		return p1->compare(p2) == LOWER;
+	});
+
+	size_t index1, index2;
+	for (size_t i = 0; i < packets.size(); i++){
+		Packet* p = packets[i];
+		if (p == firstAdd)
+			index1 = i;
+		if (p == secondAdd)
+			index2 = i;
+	}
+
+	delete firstAdd;
+	delete secondAdd;
+
+	size_t result = (index1 + 1) * (index2 + 1);
+	return to_string(result);
+}
+
+vector<Day13::PacketPair> Day13::parsePacketPairs() {
+	vector<PacketPair> packetPairs;
+
+	for (size_t line = 0; line < input.size(); line += 3){
+		Packet* p1 = Packet::parse(input[line]);
+		Packet* p2 = Packet::parse(input[line + 1]);
+		packetPairs.emplace_back(p1, p2);
+	}
+
+	return packetPairs;
+}
+
+Day13::Packet* Day13::Packet::parse(const string &raw) {
+	if (raw.starts_with('[')){
+		auto P = new ListPacket();
+		size_t pos = 1;
+		while (pos < raw.size()){
+			size_t startPos = pos;
+			vector<char> stack;
+			while ((raw[pos] != ',' || !stack.empty()) && pos < raw.size() - 1){
+				char cur = raw[pos++];
+				if (cur == '[') stack.push_back(cur);
+				if (cur == ']') stack.pop_back();
+			}
+			if (pos > startPos)
+				P->subPackets.push_back(Day13::Packet::parse(raw.substr(startPos, pos - startPos)));
+			pos++;
+		}
+		return P;
+	} else {
+		auto P = new IntPacket();
+		P->value = stoi(raw);
+		return P;
+	}
+}
+
+Day13::CompResult Day13::ListPacket::compare(Day13::Packet *other) {
+	if (auto* list = dynamic_cast<Day13::ListPacket*>(other)){
+		size_t index_left = 0;
+		size_t index_right = 0;
+
+		while (index_left < subPackets.size() && index_right < list->subPackets.size()){
+			CompResult result = subPackets[index_left++]->compare(list->subPackets[index_right++]);
+			if (result != EQUAL)
+				return result;
+		}
+		if (index_left < subPackets.size())
+			return HIGHER;
+		if (index_right < list->subPackets.size())
+			return LOWER;
+
+		return EQUAL;
+	}
+	if (auto* intP = dynamic_cast<Day13::IntPacket*>(other)){
+		auto otherList = Day13::ListPacket::FromIntPacket(intP);
+		CompResult result = compare(otherList);
+		delete otherList;
+		return result;
+	}
+	return EQUAL;
+}
+
+Day13::ListPacket *Day13::ListPacket::FromIntPacket(Day13::IntPacket *intPacket) {
+	auto P = new Day13::ListPacket();
+	P->subPackets.push_back(intPacket);
+	return P;
+}
+
+Day13::CompResult Day13::IntPacket::compare(Day13::Packet *other) {
+	if (auto* intP = dynamic_cast<Day13::IntPacket*>(other)){
+		if (value < intP->value)
+			return LOWER;
+		if (value > intP->value)
+			return HIGHER;
+		return EQUAL;
+	}
+	if (auto* list = dynamic_cast<Day13::ListPacket*>(other)){
+		auto thisAsList = Day13::ListPacket::FromIntPacket(this);
+		CompResult result = thisAsList->compare(list);
+		delete thisAsList;
+		return result;
+	}
+	return EQUAL;
+}
diff --git a/src/days/13/Day13.h b/src/days/13/Day13.h
index 141861d..56932bf 100644
--- a/src/days/13/Day13.h
+++ b/src/days/13/Day13.h
@@ -3,6 +3,30 @@
 #include "../../Day.h"
 
 class Day13 : public Day {
+
+	enum CompResult {LOWER, HIGHER, EQUAL};
+
+	struct ListPacket;
+	struct IntPacket;
+
+	struct Packet {
+		virtual CompResult compare(Packet* other) { return CompResult::EQUAL; };
+		static Packet* parse(const string &raw);
+	};
+	struct ListPacket : Packet {
+		CompResult compare(Packet*) override;
+		vector<Packet*> subPackets;
+		static ListPacket* FromIntPacket(IntPacket*);
+	};
+	struct IntPacket : Packet {
+		CompResult compare(Packet*) override;
+		int value = 0;
+	};
+
+	typedef pair<Packet*, Packet*> PacketPair;
+
+	vector<PacketPair> parsePacketPairs();
+
 protected:
 	Result Task1() override;