aocpp/2022/10.cpp

#include <cstdint>
#include <iostream>
#include <sstream>
#include <stdexcept>
#include <string>
#include <vector>

#include <doctest.h>

#include <aocpp/Startup.hpp>

namespace {

auto Execute(std::istream & in) -> std::vector<std::int64_t>
{
  std::int64_t x {1}; // current register value (defined to start at 1)
  std::int64_t d; // change in register value
  std::string instruction;
  std::vector<std::int64_t> snapshots;

  while (in >> instruction) {
    snapshots.push_back(x);
    if ("addx" == instruction) {
      snapshots.push_back(x);
      if (!(in >> d)) {
        throw std::runtime_error{"missing operand"};
      }
      x += d;
    } else if ("noop" != instruction) {
      throw std::runtime_error{"bad instruction"};
    }
  }
  return snapshots;
}

auto Part1(std::vector<std::int64_t> const& snapshots) -> std::int64_t
{
  std::int64_t result {0};
  for (auto i : {20,60,100,140,180,220}) {
    result += i * snapshots[i-1];
  }
  return result;
}

auto Part2(std::vector<std::int64_t> const& snapshots, std::ostream & out) -> void
{
  auto constexpr rows {6};
  auto constexpr cols {40};

  if (snapshots.size() < rows * cols) {
    throw std::runtime_error{"snapshots too short"};
  }

  auto cursor = snapshots.begin();
  for (int r = 0; r < rows; r++) {
    for (int c = 0; c < cols; c++) {
      auto const d = *cursor++ - c;
      out << (-1 <= d && d <= 1 ? "█" : "░");
    }
    out << std::endl;
  }
}

} // namespace

TEST_SUITE("2022-10 examples") {
  TEST_CASE("example") {
    std::istringstream in {
      "addx 15\naddx -11\naddx 6\naddx -3\naddx 5\naddx -1\naddx -8\naddx 13\naddx 4\nnoop\n"
      "addx -1\naddx 5\naddx -1\naddx 5\naddx -1\naddx 5\naddx -1\naddx 5\naddx -1\naddx -35\n"
      "addx 1\naddx 24\naddx -19\naddx 1\naddx 16\naddx -11\nnoop\nnoop\naddx 21\naddx -15\n"
      "noop\nnoop\naddx -3\naddx 9\naddx 1\naddx -3\naddx 8\naddx 1\naddx 5\nnoop\nnoop\nnoop\n"
      "noop\nnoop\naddx -36\nnoop\naddx 1\naddx 7\nnoop\nnoop\nnoop\naddx 2\naddx 6\nnoop\n"
      "noop\nnoop\nnoop\nnoop\naddx 1\nnoop\nnoop\naddx 7\naddx 1\nnoop\naddx -13\naddx 13\n"
      "addx 7\nnoop\naddx 1\naddx -33\nnoop\nnoop\nnoop\naddx 2\nnoop\nnoop\nnoop\naddx 8\nnoop\n"
      "addx -1\naddx 2\naddx 1\nnoop\naddx 17\naddx -9\naddx 1\naddx 1\naddx -3\naddx 11\nnoop\n"
      "noop\naddx 1\nnoop\naddx 1\nnoop\nnoop\naddx -13\naddx -19\naddx 1\naddx 3\naddx 26\n"
      "addx -30\naddx 12\naddx -1\naddx 3\naddx 1\nnoop\nnoop\nnoop\naddx -9\naddx 18\naddx 1\n"
      "addx 2\nnoop\nnoop\naddx 9\nnoop\nnoop\nnoop\naddx -1\naddx 2\naddx -37\naddx 1\naddx 3\n"
      "noop\naddx 15\naddx -21\naddx 22\naddx -6\naddx 1\nnoop\naddx 2\naddx 1\nnoop\naddx -10\n"
      "noop\nnoop\naddx 20\naddx 1\naddx 2\naddx 2\naddx -6\naddx -11\nnoop\nnoop\nnoop\n"
    };
    
    auto snapshots = Execute(in);
    CHECK(13140 == Part1(snapshots));
    std::ostringstream out;
    Part2(snapshots, out);
    CHECK(out.str() ==
      "██░░██░░██░░██░░██░░██░░██░░██░░██░░██░░\n"
      "███░░░███░░░███░░░███░░░███░░░███░░░███░\n"
      "████░░░░████░░░░████░░░░████░░░░████░░░░\n"
      "█████░░░░░█████░░░░░█████░░░░░█████░░░░░\n"
      "██████░░░░░░██████░░░░░░██████░░░░░░████\n"
      "███████░░░░░░░███████░░░░░░░███████░░░░░\n"
    );
  }
}

auto Main(std::istream & in, std::ostream & out) -> void
{
  auto const snapshots {Execute(in)};
  out << "Part 1: " << Part1(snapshots) << std::endl;
  Part2(snapshots, out << "Part 2:\n");
}