aocpp/2019/14.cpp

#include <algorithm>
#include <cstdint>
#include <iostream>
#include <sstream>
#include <iterator>
#include <numeric>
#include <map>
#include <set>
#include <vector>
#include <tuple>

#include <doctest.h>

#include <aocpp/Startup.hpp>

namespace {

using Recipes = std::map<std::string, std::pair<std::int64_t, std::vector<std::pair<std::int64_t, std::string>>>>;

auto Parse(std::istream & in) -> Recipes {
  Recipes result;

  std::string line;

  std::int64_t n;
  std::string word;

  while (std::getline(in, line)) {
    std::vector<std::pair<std::int64_t, std::string>> components;
    std::istringstream sin {line};

    bool leftSide;
    do {
      sin >> n >> word;
      leftSide = word.back() == ',';
      if (leftSide) word.pop_back();
      components.push_back({n, word});
    } while(leftSide);
    sin >> word; // skip
    sin >> n >> word;
    result.insert({word, {n, std::move(components)}});
  }

  return result;
}

auto Topsort(Recipes const& recipes) -> std::vector<std::string>
{
  // Kahn's algorithm
  std::vector<std::string> result;
  result.reserve(recipes.size());

  std::map<std::string, bool> marks; // false temp, true done
  auto const visit = [&](auto const& visit, auto const& name) -> void {
    auto [mark_iterator, is_new] = marks.try_emplace(name, false);
    auto& [_, is_done] = *mark_iterator;

    if (is_new) {
      auto const rit = recipes.find(name);
      if (rit != recipes.end()) {
        for (auto const& [_, c] : rit->second.second) {
          visit(visit, c);
        }
      }
      is_done = true;
      result.push_back(name);
    } else if (!is_done) {
      throw std::runtime_error{"cyclic graph"};
    }
  };

  for (auto const& [c,_] : recipes) {
    visit(visit, c);
  }

  std::reverse(result.begin(), result.end());

  return result;
}

class Machine {
  struct Entry {
    std::int64_t need;
    std::int64_t batch;
    std::vector<std::pair<std::int64_t, std::int64_t&>> components;
  };
  std::int64_t ore_;
  std::vector<Entry> process_;
public:
  Machine(Recipes const& recipes)
  {
    auto order = Topsort(recipes);
    order.pop_back();
    process_.resize(order.size(), {});

    std::map<std::string, std::size_t> indexes;
    for (auto && name : order) {
      indexes.insert({name, indexes.size()});
    }

    for (auto && [k,v] : recipes) {
      auto & entry = process_[indexes[k]];
      entry.batch = v.first;
      for (auto && [m,c] : v.second) {
        entry.components.push_back({m, c == "ORE" ? ore_ : process_[indexes[c]].need});
      }
    }
  }

  auto operator()(std::int64_t fuel) {
    for (auto && entry : process_) {
      entry.need = 0;
    }
    process_[0].need = fuel;
    ore_ = 0;

    for (auto && entry : process_) {
      auto batches = (entry.need + entry.batch - 1) / entry.batch;
      for (auto && [m,c] : entry.components) {
        c += batches*m;
      }
    }

    return ore_;
  }
};

auto ComputeFuel(Machine & machine, std::int64_t ore) {
  std::int64_t tooHi = 1;
  while (machine(tooHi) <= ore) {
    tooHi *= 2;
  }

  std::int64_t lo = 0;
  while (lo+1 != tooHi) {
    auto mid = std::midpoint(lo, tooHi);
    (machine(mid) > ore ? tooHi : lo) = mid;
  }

  return lo;
}

} // namespace

TEST_SUITE("documented examples") {
  TEST_CASE("a") {
    std::istringstream in {
      "10 ORE => 10 A\n"
      "1 ORE => 1 B\n"
      "7 A, 1 B => 1 C\n"
      "7 A, 1 C => 1 D\n"
      "7 A, 1 D => 1 E\n"
      "7 A, 1 E => 1 FUEL\n"};
    Machine m{Parse(in)};
    REQUIRE(m(1) == 31);
  }

  TEST_CASE("b") {
    std::istringstream in {
      "9 ORE => 2 A\n"
      "8 ORE => 3 B\n"
      "7 ORE => 5 C\n"
      "3 A, 4 B => 1 AB\n"
      "5 B, 7 C => 1 BC\n"
      "4 C, 1 A => 1 CA\n"
      "2 AB, 3 BC, 4 CA => 1 FUEL\n"};
    Machine m{Parse(in)};
    REQUIRE(m(1) == 165);
  }

  TEST_CASE("c") {
    std::istringstream in {
      "157 ORE => 5 NZVS\n"
      "165 ORE => 6 DCFZ\n"
      "44 XJWVT, 5 KHKGT, 1 QDVJ, 29 NZVS, 9 GPVTF, 48 HKGWZ => 1 FUEL\n"
      "12 HKGWZ, 1 GPVTF, 8 PSHF => 9 QDVJ\n"
      "179 ORE => 7 PSHF\n"
      "177 ORE => 5 HKGWZ\n"
      "7 DCFZ, 7 PSHF => 2 XJWVT\n"
      "165 ORE => 2 GPVTF\n"
      "3 DCFZ, 7 NZVS, 5 HKGWZ, 10 PSHF => 8 KHKGT\n"};
    Machine m{Parse(in)};
    REQUIRE(m(1) == 13312);
    REQUIRE(ComputeFuel(m, 1'000'000'000'000) == 82892753);
  }

  TEST_CASE("d") {
    std::istringstream in {
      "2 VPVL, 7 FWMGM, 2 CXFTF, 11 MNCFX => 1 STKFG\n"
      "17 NVRVD, 3 JNWZP => 8 VPVL\n"
      "53 STKFG, 6 MNCFX, 46 VJHF, 81 HVMC, 68 CXFTF, 25 GNMV => 1 FUEL\n"
      "22 VJHF, 37 MNCFX => 5 FWMGM\n"
      "139 ORE => 4 NVRVD\n"
      "144 ORE => 7 JNWZP\n"
      "5 MNCFX, 7 RFSQX, 2 FWMGM, 2 VPVL, 19 CXFTF => 3 HVMC\n"
      "5 VJHF, 7 MNCFX, 9 VPVL, 37 CXFTF => 6 GNMV\n"
      "145 ORE => 6 MNCFX\n"
      "1 NVRVD => 8 CXFTF\n"
      "1 VJHF, 6 MNCFX => 4 RFSQX\n"
      "176 ORE => 6 VJHF\n"};
    Machine m{Parse(in)};
    REQUIRE(m(1) == 180697);
    REQUIRE(ComputeFuel(m, 1'000'000'000'000) == 5586022);
  }

  TEST_CASE("e") {
    std::istringstream in {
      "171 ORE => 8 CNZTR\n"
      "7 ZLQW, 3 BMBT, 9 XCVML, 26 XMNCP, 1 WPTQ, 2 MZWV, 1 RJRHP => 4 PLWSL\n"
      "114 ORE => 4 BHXH\n"
      "14 VRPVC => 6 BMBT\n"
      "6 BHXH, 18 KTJDG, 12 WPTQ, 7 PLWSL, 31 FHTLT, 37 ZDVW => 1 FUEL\n"
      "6 WPTQ, 2 BMBT, 8 ZLQW, 18 KTJDG, 1 XMNCP, 6 MZWV, 1 RJRHP => 6 FHTLT\n"
      "15 XDBXC, 2 LTCX, 1 VRPVC => 6 ZLQW\n"
      "13 WPTQ, 10 LTCX, 3 RJRHP, 14 XMNCP, 2 MZWV, 1 ZLQW => 1 ZDVW\n"
      "5 BMBT => 4 WPTQ\n"
      "189 ORE => 9 KTJDG\n"
      "1 MZWV, 17 XDBXC, 3 XCVML => 2 XMNCP\n"
      "12 VRPVC, 27 CNZTR => 2 XDBXC\n"
      "15 KTJDG, 12 BHXH => 5 XCVML\n"
      "3 BHXH, 2 VRPVC => 7 MZWV\n"
      "121 ORE => 7 VRPVC\n"
      "7 XCVML => 6 RJRHP\n"
      "5 BHXH, 4 VRPVC => 5 LTCX\n"};
    Machine m{Parse(in)};
    REQUIRE(m(1) == 2210736);
    REQUIRE(ComputeFuel(m, 1'000'000'000'000) == 460664);
  }
}

auto main(int argc, char** argv) -> int {
  auto recipes = Parse(*aocpp::Startup(argc, argv));
  auto machine = Machine(recipes);
  auto part1 = machine(1);
  auto part2 = ComputeFuel(machine, 1'000'000'000'000);
  std::cout << "Part 1: " << part1 << std::endl;
  std::cout << "Part 2: " << part2 << std::endl;
}