day8a.cpp

#include <string>
#include <vector>
#include <sstream>
#include <fstream>
#include <cassert>
#include <algorithm>
#include <array>
#include <iostream>
#include <set>

namespace day8a
{
	int main()
	{
		// BEGIN BOILERPLATE
		std::string input0;
		//std::ifstream ifile("day8_sample.txt");
		std::ifstream ifile("day8.txt");
		if (ifile.is_open())
		{
			while (!ifile.eof())
			{
				std::string line;
				std::getline(ifile, line);
				input0 += line + '\n';
			}
			assert(input0.back() == '\n');
			input0.pop_back(); // no trailing newline character please
			//__debugbreak();
		}
		else
		{
			assert(0);
		}

		std::vector<std::string> values;
		std::string temp;
		for (char c : input0)
		{
			if (c == '\n')
			{
				values.push_back(temp);
				temp = "";
				continue;
			}
			temp += c;
		}
		values.push_back(temp);

		struct coordinate
		{
			int x;
			int y;
			int z;
			coordinate(int xx, int yy, int zz) // because we are using C++14 with emplace_back we don't have improved aggregate initialization ;(
			{
				x = xx;
				y = yy;
				z = zz;
			}
			double distance(const coordinate& c)
			{
				double dx = x - c.x;
				double dy = y - c.y;
				double dz = z - c.z;
				return std::sqrt(dx * dx + dy * dy + dz * dz);
			}
			bool operator<(const coordinate& c) const // forgot to make it const...
			{
				bool test;
				if (x < c.x)
					test = true;
				else if (c.x < x) // it's supposed to be other is LESS than!!!
					test = false;
				else if (y < c.y)
					test = true;
				else if (c.y < y)
					test = false;
				else if (z < c.z)
					test = true;
				else if (c.z < z)
					test = false;
				else
					test = false;
				
				bool test2;

				if (x != c.x)
					test2 = x < c.x;
				else if (y != c.y)
					test2 = y < c.y;
				else
					test2 = z < c.z;

				if (test != test2)
					__debugbreak();

				return test;
			}
		};

		std::vector<coordinate> coordinates;
		for (auto& s : values)
		{
			int x;
			int y;
			int z;
			char c;
			std::istringstream iss{ s };
			iss >> x;
			iss >> c;
			iss >> y;
			iss >> c;
			iss >> z;
			coordinates.emplace_back( x, y, z );
		}

		struct distance_pair
		{
			double distance;
			int i;
			int j;
		};
		std::vector<distance_pair> distances2;

		for (int i = 0; i < coordinates.size() - 1; i++)
		{
			for (int j = i + 1; j < coordinates.size(); j++)
			{
				distance_pair d;
				d.distance = coordinates[i].distance(coordinates[j]);
				d.i = i;
				d.j = j;
				distances2.push_back(d);
			}
		}
		std::sort(distances2.begin(), distances2.end(), [](auto& a, auto& b) -> bool { return a.distance < b.distance; });

		std::vector<std::set<coordinate>> circuits;
		for (int i = 0; i < 1000; i++)
		{
			std::set<coordinate> s;
			int i0 = distances2[i].i;
			int i1 = distances2[i].j;
			auto c0 = coordinates[i0];
			auto c1 = coordinates[i1];
			s.insert(c0);
			s.insert(c1);
			circuits.push_back(s);
		}

		for (int i = 0; i < circuits.size() - 1; i++)
		{
			for (int j = i + 1; j < circuits.size(); j++)
			{
				auto& c0 = circuits[i];
				auto& c1 = circuits[j];
				auto c2 = c0;
				c2.insert(c1.begin(), c1.end());
				if (c2.size() < c0.size() + c1.size())
				{
					circuits.erase(circuits.begin() + j);
					circuits.erase(circuits.begin() + i);
					circuits.push_back(c2);
					i--;
					break;
				}

			}
		}

		std::sort(circuits.begin(), circuits.end(), [](auto& a, auto& b) -> bool { return a.size() < b.size(); });

		int result =
			(circuits.end() - 1)->size() *
			(circuits.end() - 2)->size() *
			(circuits.end() - 3)->size();

		// 769 * 7 * 4 = 21532 TOO LOW
		__debugbreak();
		return 0;
	}

}