day2a.cpp

#include <string>
#include <vector>
#include <sstream>
#include <fstream>
#include <cassert>

namespace day2a
{
	// an invalid id has an even number of digits
	// the first half matches the second half

	int main()
	{
		std::string input0;
		//std::ifstream ifile("day2a_sample.txt");
		std::ifstream ifile("day2a.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 == '-' || c == ',')
			{
				values.push_back(temp);
				temp = "";
				continue;
			}
			temp += c;
		}
		values.push_back(temp);

		std::vector<std::pair<uint64_t, uint64_t>> ranges;
		for (int i = 0; i < values.size(); i += 2)
		{
			ranges.emplace_back(
				std::stoull(values[i]),
				std::stoull(values[i + 1])
			);
		}

		std::vector<uint64_t> ranges2;
		for (auto& r : ranges)
		{
			for (uint64_t i = r.first; i <= r.second; i++)
			{
				ranges2.push_back(i);
			}
		}

		uint64_t accumulator = 0;
		for (auto v : ranges2)
		{
			int digits = std::floor(std::log10(v)) + 1;
			if (digits % 2 == 0)
			{
				uint64_t top = v % static_cast<uint64_t>(std::powl(10, digits / 2));
				uint64_t bot = v / static_cast<uint64_t>(std::powl(10, digits / 2));
				if (top == bot)
					accumulator += v;
			}
		}

		__debugbreak();
		return 0;
	}

}