18
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2019/18.cpp
56
2019/18.cpp
@ -94,7 +94,7 @@ auto FindDistances(Map const& map, Features const& features) -> Distances {
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Distances distances;
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for (auto && [start_letter, start_coord] : features) {
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if (islower(start_letter) || start_letter == '@') {
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if (!std::isupper(start_letter)) {
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FindDistancesFrom(map, features, distances, start_letter, start_coord);
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}
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}
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@ -102,12 +102,6 @@ auto FindDistances(Map const& map, Features const& features) -> Distances {
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return distances;
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}
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struct P1S {
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char location;
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unsigned long long keys;
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auto operator<=>(P1S const&) const = default;
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};
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auto HasKey(Doors doors, char key) {
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return doors.test(std::toupper(key) - 'A');
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}
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@ -116,26 +110,31 @@ auto SetKey(Doors doors, char key) {
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return doors.set(std::toupper(key) - 'A');
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}
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auto Part1(Distances const& distances) -> std::int64_t {
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std::set<P1S> seen;
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std::multimap<std::int64_t, std::pair<char, Doors>> todo
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{{0, {'@', Doors()}}};
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auto SolveMaze(Distances const& distances, std::set<char> const initial_locations) -> std::int64_t {
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// Track current positions and current set of keys in easy to compare form
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using Visited = std::pair<std::set<char>, unsigned long long>;
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std::set<Visited> seen;
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std::multimap<std::int64_t, std::pair<std::set<char>, Doors>> todo
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{{0, {initial_locations, Doors()}}};
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while (!todo.empty()) {
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auto it = todo.begin();
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auto [steps, ld] = *it;
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auto& [l,keys] = ld;
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auto& [locations,keys] = ld;
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todo.erase(it);
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if (keys.all()) { return steps; }
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if (seen.insert({l,keys.to_ullong()}).second) {
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auto dit = distances.find(l);
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if (dit != distances.end()) {
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for (auto && [next, costneed] : dit->second) {
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if (seen.insert({locations,keys.to_ullong()}).second) {
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for (auto location : locations) {
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auto locations1 = locations; locations1.erase(location);
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for (auto && [next, costneed] : distances.at(location)) {
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auto [cost, need] = costneed;
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if ((need & (~keys)).none()) {
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todo.insert({steps + cost, {next, SetKey(keys, next)}});
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if ((need & ~keys).none()) {
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auto locations2 = locations1; locations2.insert(next);
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todo.insert({steps + cost, {locations2, SetKey(keys, next)}});
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}
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}
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}
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@ -145,6 +144,20 @@ auto Part1(Distances const& distances) -> std::int64_t {
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throw std::runtime_error{"no solution to part 1"};
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}
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auto UpdateMap(Map& map, Features & features) {
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auto start = features['@'];
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map[start.y][start.x] = '#';
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map[start.y][start.x+1] = '#';
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map[start.y][start.x-1] = '#';
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map[start.y+1][start.x] = '#';
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map[start.y-1][start.x] = '#';
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features.erase('@');
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features['^'] = Up(Left(start));
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features['&'] = Down(Left(start));
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features['*'] = Up(Right(start));
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features['$'] = Down(Right(start));
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}
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} // namespace
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auto main(int argc, char** argv) -> int {
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@ -152,6 +165,9 @@ auto main(int argc, char** argv) -> int {
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auto features = FindFeatures(map);
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auto distances = FindDistances(map, features);
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std::cout << "Part 1: " << Part1(distances) << std::endl;
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//std::cout << "Part 2: " << part2 << std::endl;
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std::cout << "Part 1: " << SolveMaze(distances, {'@'}) << std::endl;
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UpdateMap(map, features);
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distances = FindDistances(map, features);
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std::cout << "Part 2: " << SolveMaze(distances, {'^', '&', '*', '$'}) << std::endl;
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}
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