174 lines
4.3 KiB
C++
174 lines
4.3 KiB
C++
#include <algorithm>
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#include <cstdint>
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#include <iostream>
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#include <iomanip>
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#include <fstream>
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#include <iterator>
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#include <stdexcept>
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#include <vector>
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#include <set>
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#include <string>
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#include <tuple>
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#include <bitset>
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#include <deque>
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#include <cctype>
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#include <map>
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#include <aocpp/Startup.hpp>
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#include <aocpp/Coord.hpp>
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// lowercase key
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// uppercase door
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// start at @
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// wall #
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// boring .
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namespace {
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using namespace aocpp;
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using Map = std::vector<std::string>;
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using Features = std::map<char, Coord>;
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using Doors = std::bitset<26>;
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using Distances = std::map<char,std::map<char, std::pair<std::int64_t, Doors>>>;
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auto ReadMap(std::istream & in) -> Map {
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Map result;
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std::string line;
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while (std::getline(in, line)) {
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result.emplace_back(std::move(line));
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}
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return result;
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}
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auto FindFeatures(Map const& map) -> Features {
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std::map<char,Coord> features;
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for (std::int64_t y = 0; y < map.size(); y++) {
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for (std::int64_t x = 0; x < map[y].size(); x++) {
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auto c = map[y][x];
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switch (c) {
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default: features[c] = Coord{x,y};
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case '#':
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case '.': {}
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}
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}
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}
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return features;
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}
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auto FindDistancesFrom(
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Map const& map, Features const& features,
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Distances & distances,
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char start_letter, Coord start
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) {
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std::map<char, std::pair<std::int64_t, Doors>> result;
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std::set<Coord> seen;
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std::deque<std::tuple<std::int64_t, Coord, Doors>> todo
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{{0, start, {}}};
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while (!todo.empty()) {
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auto [steps, here, doors] = todo.front();
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todo.pop_front();
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if (seen.insert(here).second) {
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auto c = map[here.y][here.x];
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if (c == '#') {
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continue;
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}
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if (c != start_letter && std::islower(c)) {
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distances[start_letter][c] = {steps, doors};
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continue;
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}
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if (std::isupper(c)) {
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doors.set(c - 'A');
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}
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for (auto && fn : {Up,Down,Left,Right}) {
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auto here_ = fn(here);
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todo.push_back({steps+1, here_, doors});
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}
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}
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}
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return result;
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}
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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 (!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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return distances;
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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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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 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& [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({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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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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}
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}
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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['$'] = Down(Right(start));
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}
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} // namespace
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auto main(int argc, char** argv) -> int {
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auto map = ReadMap(Startup(argc, argv));
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auto features = FindFeatures(map);
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auto distances = FindDistances(map, features);
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std::cout << "Part 1: " << SolveMaze(distances, {'@'}) << std::endl;
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UpdateMap(map, features);
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distances = FindDistances(map, features);
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std::cout << "Part 2: " << SolveMaze(distances, {'^', '&', '*', '$'}) << std::endl;
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}
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