aocpp/2017/02.cpp

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <iostream>
#include <iterator>
#include <sstream>
#include <string>
#include <vector>

#include <doctest.h>

#include <aocpp/Startup.hpp>

namespace {

auto Omnibus(std::istream & in)
-> std::pair<std::int64_t, std::int64_t>
{
  std::string line;
  std::vector<std::int64_t> numbers;
  std::int64_t p1{0}, p2{0};

  while (std::getline(in, line)) {
    numbers.clear();

    std::istringstream inrow {std::move(line)};
    std::copy(
      std::istream_iterator<std::int64_t>{inrow},
      std::istream_iterator<std::int64_t>{},
      std::back_inserter(numbers));

    std::sort(numbers.begin(), numbers.end());

    p1 += numbers.back() - numbers.front();

    auto n = numbers.size();
    for (std::size_t i = 0; i < n; i++) {
      for (std::size_t j = i+1; j < n; j++) {
        if (numbers[j] % numbers[i] == 0) {
          p2 += numbers[j] / numbers[i];
          goto found;
        }
      }
    }
    found: {}
  }
  return {p1, p2};
}

} // namespace

TEST_SUITE("2017-02 examples") {
  TEST_CASE("part 1") {
    std::istringstream in {
      "5 1 9 5\n"
      "7 5 3\n"
      "2 4 6 8\n"};
    CHECK(Omnibus(in).first == 18);
  }
  TEST_CASE("part 2") {
    std::istringstream in {
      "5 9 2 8\n"
      "9 4 7 3\n"
      "3 8 6 5\n"};
    CHECK(Omnibus(in).second == 9);
  }
}

auto Main(std::istream & in, std::ostream & out) -> void
{
  auto const [p1,p2] = Omnibus(in);
  out << "Part 1: " << p1 << std::endl;
  out << "Part 2: " << p2 << std::endl;
}