aocpp/2022/08.cpp

#include <algorithm>
#include <cstdint>
#include <functional>
#include <iostream>
#include <numeric>
#include <sstream>
#include <vector>

#include <doctest.h>

#include <aocpp/Grid.hpp>
#include <aocpp/Coord.hpp>
#include <aocpp/Startup.hpp>

using namespace aocpp;

namespace {

using Dir = Coord(*)(Coord);
Dir directions[4] {Up, Down, Left, Right};

auto Part1(Grid const& grid) -> std::int64_t
{
  std::int64_t result {0};
  for (auto [c, v] : grid) {
    result += std::any_of(
      std::begin(directions), std::end(directions),
      [&](Dir const dir) {
        for (auto x = dir(c); grid.contains(x); x = dir(x)) {
          if (grid[x] >= v) { return false; }
        }
        return true;
      });
  }
  return result;
}

auto Part2(Grid const& grid) -> std::int64_t
{
  std::int64_t result {0};
  for (auto [c, v] : grid) {
    auto score = std::transform_reduce(
      std::begin(directions), std::end(directions),
      std::int64_t{1}, std::multiplies(), // product
      [&](Dir const dir) {
        std::int64_t count {0};
        for (auto x = dir(c); grid.contains(x); x = dir(x)) {
          count++;
          if (grid[x] >= v) break;
        }
        return count;
      });
    if (result < score) result = score;
  }
  return result;
}

} // namespace

TEST_SUITE("2022-08 examples") {
  TEST_CASE("example") {
    std::istringstream in {
      "30373\n"
      "25512\n"
      "65332\n"
      "33549\n"
      "35390\n"};
    auto grid = aocpp::Grid::Parse(in);
    CHECK(Part1(grid) == 21);
    CHECK(Part2(grid) == 8);
  }
}

auto Main(std::istream & in, std::ostream & out) -> void
{
  auto const grid = Grid::Parse(in);
  out << "Part 1: " << Part1(grid) << std::endl;
  out << "Part 2: " << Part2(grid) << std::endl;
}