aocpp/day13.cpp

#include <iostream>
#include <utility>
#include <tuple>
#include <set>

#include <intcode/intcode.hpp>
#include <intcode/Grid.hpp>
using namespace intcode;

namespace {

auto Compute1(Machine machine)
  -> std::size_t {
  std::set<Coord> screen;

  for (;;) {
    auto effect = Step(machine);
    if (std::holds_alternative<Halt>(effect)) {
      return screen.size();
    }
    auto x = std::get<Output>(effect).val;
    auto y = std::get<Output>(Step(machine)).val;
    auto v = std::get<Output>(Step(machine)).val;

    if (2 == v) { screen.insert({x,y}); } else { screen.erase({x,y}); }
  }
}

auto Compute2(Machine machine) {
  ValueType score {0};
  ValueType paddleX {0};
  ValueType ballX {0};

  machine.At(0) = 2;
  for(;;) {
    auto effect = Step(machine);
    if (std::holds_alternative<Halt>(effect)) {
      return score;
    } else if (auto i = std::get_if<Input>(&effect)) {
      i->pos = paddleX < ballX ? 1
             : paddleX > ballX ? -1 : 0;
    } else {
      auto x = std::get<Output>(effect).val;
      auto y = std::get<Output>(Step(machine)).val;
      auto v = std::get<Output>(Step(machine)).val;

      if (-1 == x && 0 == y) {
        score = v;
      } else {
        switch (v) {
          case 3: // paddle
            paddleX = x;
            break;
          case 4: // ball
            ballX = x;
            break;
        }
      }
    }
  }
}

} // namespace

auto main() -> int {
  auto machine = Machine{ParseStream(std::cin)};
  std::cout << "Part 1: " << Compute1(machine) << std::endl;
  std::cout << "Part 2: " << Compute2(std::move(machine)) << std::endl;
}