2023 Day 16
This commit is contained in:
172
2023/puzzle-16-01.cc
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172
2023/puzzle-16-01.cc
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <functional>
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#include <iostream>
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#include <list>
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#include <string>
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#include <unordered_set>
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#include <utility>
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#include <vector>
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using Int = std::int64_t;
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using UInt = std::uint64_t;
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using Location = std::pair<Int, Int>;
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using Direction = std::pair<Int, Int>;
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constexpr Direction north = std::make_pair(0, -1);
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constexpr Direction east = std::make_pair(1, 0);
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constexpr Direction south = std::make_pair(0, 1);
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constexpr Direction west = std::make_pair(-1, 0);
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auto operator+(Location const& loc, Direction const& dir) -> Location
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{
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return std::make_pair(loc.first + dir.first, loc.second + dir.second);
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}
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struct Beam
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{
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Beam(Location loc, Direction dir)
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: loc_(std::move(loc)), dir_(std::move(dir))
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{
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}
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[[nodiscard]] auto hash() const noexcept -> std::size_t
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{
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return std::hash<Int>{}(
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((loc_.first * 1000 + loc_.second) * 4 + (dir_.first + 1)) * 4 + (dir_.second + 1));
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}
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[[nodiscard]] auto operator==(Beam const& rhs) const noexcept -> bool
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{
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return loc_ == rhs.loc_ && dir_ == rhs.dir_;
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}
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Location loc_;
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Direction dir_;
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};
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template<>
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struct std::hash<Beam>
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{
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[[nodiscard]] auto operator()(Beam const& beam) const noexcept -> std::size_t
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{
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return beam.hash();
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}
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};
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template<>
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struct std::hash<Location>
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{
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[[nodiscard]] auto operator()(Location const& loc) const noexcept -> std::size_t
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{
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return std::hash<Int>{}(loc.first * 1000 + loc.second);
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}
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};
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struct Grid
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{
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void push_line(std::string const& line) { grid_.push_back(line); }
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[[nodiscard]] auto energised() const -> UInt
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{
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// The energised set includes directions - so we need to build a set that just includes locations.
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std::unordered_set<Location> locs;
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std::vector<std::string> energy_grid(grid_.size(), std::string(grid_[0].size(), '.'));
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for (auto const [loc, dir] : energised_) {
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locs.insert(loc);
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energy_grid[loc.second][loc.first] = '#';
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}
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for (auto const& row : energy_grid) { std::cout << row << '\n'; }
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return locs.size();
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}
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[[nodiscard]] auto loc_valid(Location const& loc) const noexcept -> bool
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{
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if (loc.first < 0) { return false; }
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if (loc.second < 0) { return false; }
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if (loc.second >= grid_.size()) { return false; }
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if (loc.first >= grid_[loc.second].size()) { return false; }
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return true;
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}
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void energise()
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{
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std::list<Beam> beams;
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beams.emplace_back(std::make_pair(0, 0), east);
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while (!beams.empty()) {
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auto beam{beams.front()};
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beams.pop_front();
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if (!loc_valid(beam.loc_)) { continue; }
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// Insert into hash of energised locations. If that fails we've done this before and don't
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// need to do it again.
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if (auto [it, success] = energised_.insert(beam); !success) { continue; }
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switch (grid_[beam.loc_.second][beam.loc_.first]) {
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case '.':
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break;
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case '\\':
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if (beam.dir_ == north) { beam.dir_ = west; }
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else if (beam.dir_ == east) { beam.dir_ = south; }
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else if (beam.dir_ == south) { beam.dir_ = east; }
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else if (beam.dir_ == west) { beam.dir_ = north; }
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else { std::abort(); }
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break;
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case '/':
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if (beam.dir_ == north) { beam.dir_ = east; }
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else if (beam.dir_ == east) { beam.dir_ = north; }
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else if (beam.dir_ == south) { beam.dir_ = west; }
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else if (beam.dir_ == west) { beam.dir_ = south; }
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else { std::abort(); }
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break;
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case '|':
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if (beam.dir_ == east || beam.dir_ == west) {
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Beam beam2{beam};
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beam2.dir_ = north;
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beam2.loc_ = beam2.loc_ + beam2.dir_;
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beams.push_back(beam2);
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beam.dir_ = south;
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}
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break;
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case '-':
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if (beam.dir_ == north || beam.dir_ == south) {
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Beam beam2{beam};
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beam2.dir_ = east;
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beam2.loc_ = beam2.loc_ + beam2.dir_;
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beams.push_back(beam2);
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beam.dir_ = west;
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}
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break;
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default:
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std::abort();
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}
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beam.loc_ = beam.loc_ + beam.dir_;
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beams.push_back(beam);
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}
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}
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private:
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std::vector<std::string> grid_;
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std::unordered_set<Beam> energised_;
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};
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auto main() -> int try {
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std::string line;
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Grid grid;
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while (std::getline(std::cin, line)) {
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grid.push_line(line);
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}
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grid.energise();
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UInt count = grid.energised();
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std::cout << "Total: " << count << '\n';
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return EXIT_SUCCESS;
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}
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catch (...) {
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std::cerr << "Uncaught exception.\n";
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return EXIT_FAILURE;
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}
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198
2023/puzzle-16-02.cc
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198
2023/puzzle-16-02.cc
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@@ -0,0 +1,198 @@
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#include <algorithm>
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#include <cstddef>
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#include <cstdint>
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#include <cstdlib>
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#include <functional>
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#include <iostream>
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#include <list>
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#include <string>
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#include <unordered_set>
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#include <utility>
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#include <vector>
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using Int = std::int64_t;
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using UInt = std::uint64_t;
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using Location = std::pair<Int, Int>;
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using Direction = std::pair<Int, Int>;
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constexpr Direction north = std::make_pair(0, -1);
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constexpr Direction east = std::make_pair(1, 0);
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constexpr Direction south = std::make_pair(0, 1);
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constexpr Direction west = std::make_pair(-1, 0);
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auto operator+(Location const& loc, Direction const& dir) -> Location
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{
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return std::make_pair(loc.first + dir.first, loc.second + dir.second);
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}
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struct Beam
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{
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Beam(Location loc, Direction dir)
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: loc_(std::move(loc)), dir_(std::move(dir))
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{
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}
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[[nodiscard]] auto hash() const noexcept -> std::size_t
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{
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return std::hash<Int>{}(
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((loc_.first * 1000 + loc_.second) * 4 + (dir_.first + 1)) * 4 + (dir_.second + 1));
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}
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[[nodiscard]] auto operator==(Beam const& rhs) const noexcept -> bool
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{
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return loc_ == rhs.loc_ && dir_ == rhs.dir_;
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}
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Location loc_;
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Direction dir_;
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};
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template<>
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struct std::hash<Beam>
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{
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[[nodiscard]] auto operator()(Beam const& beam) const noexcept -> std::size_t
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{
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return beam.hash();
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}
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};
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template<>
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struct std::hash<Location>
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{
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[[nodiscard]] auto operator()(Location const& loc) const noexcept -> std::size_t
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{
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return std::hash<Int>{}(loc.first * 1000 + loc.second);
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}
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};
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struct Grid
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{
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void push_line(std::string const& line) { grid_.push_back(line); }
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[[nodiscard]] auto max_energised() -> UInt
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{
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UInt max{0};
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for (unsigned x{0}; x < grid_[0].size(); ++x) {
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energised_.clear();
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energise(Beam(std::make_pair(x, 0), south));
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max = std::max(max, energised());
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}
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for (unsigned y{0}; y < grid_.size(); ++y) {
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energised_.clear();
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energise(Beam(std::make_pair(0, y), east));
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max = std::max(max, energised());
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energised_.clear();
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energise(Beam(std::make_pair(grid_[y].size() - 1, y), west));
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max = std::max(max, energised());
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}
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auto max_y{grid_.size() - 1};
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for (unsigned x{0}; x < grid_[max_y].size(); ++x) {
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energised_.clear();
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energise(Beam(std::make_pair(x, max_y), north));
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max = std::max(max, energised());
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}
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return max;
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}
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private:
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[[nodiscard]] auto energised() const -> UInt
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{
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// The energised set includes directions - so we need to build a set that just includes locations.
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std::unordered_set<Location> locs;
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for (auto const [loc, dir] : energised_) {
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locs.insert(loc);
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}
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return locs.size();
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}
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[[nodiscard]] auto loc_valid(Location const& loc) const noexcept -> bool
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{
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if (loc.first < 0) { return false; }
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if (loc.second < 0) { return false; }
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if (loc.second >= grid_.size()) { return false; }
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if (loc.first >= grid_[loc.second].size()) { return false; }
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return true;
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}
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void energise(Beam const& start)
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{
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std::list<Beam> beams;
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beams.push_back(start);
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while (!beams.empty()) {
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auto beam{beams.front()};
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beams.pop_front();
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if (!loc_valid(beam.loc_)) { continue; }
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// Insert into hash of energised locations. If that fails we've done this before and don't
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// need to do it again.
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if (auto [it, success] = energised_.insert(beam); !success) { continue; }
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switch (grid_[beam.loc_.second][beam.loc_.first]) {
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case '.':
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break;
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case '\\':
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if (beam.dir_ == north) { beam.dir_ = west; }
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else if (beam.dir_ == east) { beam.dir_ = south; }
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else if (beam.dir_ == south) { beam.dir_ = east; }
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else if (beam.dir_ == west) { beam.dir_ = north; }
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else { std::abort(); }
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break;
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case '/':
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if (beam.dir_ == north) { beam.dir_ = east; }
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else if (beam.dir_ == east) { beam.dir_ = north; }
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else if (beam.dir_ == south) { beam.dir_ = west; }
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else if (beam.dir_ == west) { beam.dir_ = south; }
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else { std::abort(); }
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break;
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case '|':
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if (beam.dir_ == east || beam.dir_ == west) {
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Beam beam2{beam};
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beam2.dir_ = north;
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beam2.loc_ = beam2.loc_ + beam2.dir_;
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beams.push_back(beam2);
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beam.dir_ = south;
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}
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break;
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case '-':
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if (beam.dir_ == north || beam.dir_ == south) {
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Beam beam2{beam};
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beam2.dir_ = east;
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beam2.loc_ = beam2.loc_ + beam2.dir_;
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beams.push_back(beam2);
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beam.dir_ = west;
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}
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break;
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default:
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std::abort();
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}
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beam.loc_ = beam.loc_ + beam.dir_;
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beams.push_back(beam);
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}
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}
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std::vector<std::string> grid_;
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std::unordered_set<Beam> energised_;
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};
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auto main() -> int try {
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std::string line;
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Grid grid;
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while (std::getline(std::cin, line)) {
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grid.push_line(line);
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}
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UInt max = grid.max_energised();
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std::cout << "Total: " << max << '\n';
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return EXIT_SUCCESS;
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}
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catch (...) {
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std::cerr << "Uncaught exception.\n";
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return EXIT_FAILURE;
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}
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