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360
2020/puzzle-20-02.cc
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360
2020/puzzle-20-02.cc
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#include <algorithm>
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#include <array>
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#include <cassert>
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#include <iostream>
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#include <list>
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#include <map>
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#include <regex>
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#include <set>
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#include <string>
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#include <tuple>
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using Id = unsigned long;
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using Hash = unsigned long;
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enum Edge { Top, Left, Bottom, Right };
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struct PictureArray;
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struct Picture {
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Picture(std::string id, std::istream &is) : in_use_(false) {
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assert(id.substr(0, 5) == "Tile ");
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id_ = std::stoul(id.substr(5));
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std::string line;
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while (std::getline(is, line)) {
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if (line.empty()) {
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return;
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}
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rows_.push_back(line);
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}
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}
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Picture(PictureArray const &array);
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Picture(Picture const &) = delete;
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Picture &operator=(Picture const &) = delete;
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Picture(Picture &&) = default;
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Picture &operator=(Picture &&) = default;
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void flip() {
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for (auto &r : rows_) {
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std::reverse(r.begin(), r.end());
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}
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}
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void rotate() {
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std::vector<std::string> copy(rows_.size());
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for (auto const &r : rows_) {
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std::size_t off = copy.size();
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assert(r.size() == copy.size());
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for (auto c : r) {
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copy[--off] += c;
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}
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assert(off == 0);
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}
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rows_ = copy;
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}
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Hash hash(Edge edge) const {
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unsigned x = (edge == Edge::Right) ? rows_[0].size() - 1 : 0;
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unsigned y = (edge == Edge::Bottom) ? rows_.size() - 1 : 0;
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unsigned dx = (edge == Edge::Top || edge == Edge::Bottom) ? 1 : 0;
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unsigned dy = (edge == Edge::Left || edge == Edge::Right) ? 1 : 0;
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Hash hash = 0;
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for (unsigned i = 0; i < rows_.size(); ++i) {
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hash <<= 1;
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hash |= (rows_[y][x] == '#');
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y += dy;
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x += dx;
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}
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return hash;
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}
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Id id() const noexcept { return id_; }
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bool operator<(Picture const &pict) const noexcept { return id_ < pict.id_; }
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bool operator==(Picture const &pict) const noexcept {
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return id_ == pict.id_;
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}
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bool in_use() const noexcept { return in_use_; }
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void use() noexcept { in_use_ = true; }
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void release() noexcept { in_use_ = false; }
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friend std::ostream &operator<<(std::ostream &os, Picture const &pict);
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unsigned find_monsters() {
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for (unsigned r = 0; r < 4; ++r) {
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rotate();
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for (unsigned f = 0; f < 2; ++f) {
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flip();
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auto monster_count = find_monsters1();
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if (monster_count > 0) {
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return monster_count;
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}
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}
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}
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return 0;
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}
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unsigned roughness() const {
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unsigned rough = 0;
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for (auto const &r : rows_) {
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for (auto c : r) {
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if (c == '#') {
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++rough;
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}
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}
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}
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return rough;
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}
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private:
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unsigned find_monsters1() {
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// 0 1
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// 01234567890123456789
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// #
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// # ## ## ###
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// # # # # # #
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static const std::string::size_type locs[] = {18,
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std::string::npos,
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0,
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5,
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6,
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11,
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12,
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17,
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18,
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19,
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std::string::npos,
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1,
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4,
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7,
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10,
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13,
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16,
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std::string::npos,
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std::string::npos};
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static const std::string::size_type mwidth = 20;
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static const std::size_t mheight = 3;
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unsigned monster_count = 0;
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for (std::size_t y = 0; y <= rows_.size() - mheight; ++y) {
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for (std::string::size_type x = 0; x <= rows_[y].size() - mwidth; ++x) {
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std::size_t cy = 0;
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std::string::size_type const *cx = locs;
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bool found = true;
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while (cy < mheight) {
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if (*cx == std::string::npos) {
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++cy;
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} else if (rows_[y + cy][x + *cx] != '#') {
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found = false;
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break;
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}
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++cx;
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}
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if (found) {
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++monster_count;
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std::size_t cy = 0;
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std::string::size_type const *cx = locs;
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while (cy < mheight) {
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if (*cx == std::string::npos) {
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++cy;
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} else {
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rows_[y + cy][x + *cx] = '*';
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}
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++cx;
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}
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}
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}
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}
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return monster_count;
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}
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private:
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Id id_;
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std::vector<std::string> rows_;
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bool in_use_;
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};
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std::ostream &operator<<(std::ostream &os, Picture const &pict) {
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for (auto const &r : pict.rows_) {
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os << r << '\n';
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}
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return os;
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}
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using Pictures = std::map<Id, Picture>;
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using HashMap = std::multimap<Hash, Id>;
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using Array = std::map<std::pair<unsigned, unsigned>, Id>;
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struct PictureArray {
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void add(Picture &&pic) {
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auto id = pic.id();
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auto [it, success] = pictures_.insert(std::make_pair(id, std::move(pic)));
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assert(success);
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// Set up hash -> ID mapping
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Picture &picture = it->second;
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for (unsigned r = 0; r < 4; ++r) {
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for (unsigned f = 0; f < 2; ++f) {
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hash_map_.insert({picture.hash(Edge::Top), picture.id()});
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picture.flip();
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}
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picture.rotate();
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}
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}
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Id solve() {
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assert(pictures_.size() == 9 || pictures_.size() == 144);
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for (auto &kv : pictures_) {
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if (try_position(0, 0, kv.second)) {
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print_ids();
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return piece(0, 0).id() * piece(width() - 1, 0).id() *
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piece(0, height() - 1).id() *
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piece(width() - 1, height() - 1).id();
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}
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}
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assert(false);
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return 0;
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}
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unsigned width() const noexcept {
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if (pictures_.size() == 9) {
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return 3;
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} else if (pictures_.size() == 144) {
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return 12;
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} else {
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assert(false);
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}
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return 0;
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}
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unsigned height() const noexcept { return width(); }
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Picture const &piece(unsigned x, unsigned y) const {
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auto const &it = array_.find({x, y});
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assert(it != array_.end());
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auto const &itp = pictures_.find(it->second);
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assert(itp != pictures_.end());
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return itp->second;
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}
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private:
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bool try_position(unsigned x, unsigned y, Picture &pict) {
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if (pict.in_use()) {
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return false;
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}
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auto [it, success] = array_.insert({{x, y}, pict.id()});
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if (!success) {
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it->second = pict.id();
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}
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pict.use();
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for (unsigned r = 0; r < 4; ++r) {
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pict.rotate();
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for (unsigned f = 0; f < 2; ++f) {
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pict.flip();
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if (x > 0) {
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if (piece(x - 1, y).hash(Edge::Right) != pict.hash(Edge::Left)) {
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continue;
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}
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}
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if (y > 0) {
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if (piece(x, y - 1).hash(Edge::Bottom) != pict.hash(Edge::Top)) {
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continue;
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}
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}
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auto next_x = x + 1;
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auto next_y = y;
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Hash hash = pict.hash(Edge::Right);
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if (next_x == width()) {
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next_x = 0;
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next_y = y + 1;
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hash = piece(0, y).hash(Edge::Bottom);
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}
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if (next_y == height()) {
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return true;
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}
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auto [it, ite] = hash_map_.equal_range(hash);
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while (it != ite) {
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auto itp = pictures_.find(it->second);
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assert(itp != pictures_.end());
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if (try_position(next_x, next_y, itp->second)) {
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return true;
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}
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++it;
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}
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}
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}
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pict.release();
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return false;
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}
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void print_ids() const {
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for (unsigned y = 0; y < height(); ++y) {
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for (unsigned x = 0; x < width(); ++x) {
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std::cout << " " << piece(x, y).id();
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}
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std::cout << "\n";
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}
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}
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Pictures pictures_;
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HashMap hash_map_;
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Array array_;
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};
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Picture::Picture(PictureArray const &array) : id_(0), in_use_(false) {
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for (unsigned y = 0; y < array.height(); ++y) {
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auto ybase = rows_.size();
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for (unsigned x = 0; x < array.width(); ++x) {
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auto &pict = array.piece(x, y);
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for (auto py = 1; py < pict.rows_.size() - 1; ++py) {
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auto yidx = ybase + py - 1;
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if (rows_.size() <= yidx) {
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rows_.resize(yidx + 1);
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}
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rows_[yidx] += pict.rows_[py].substr(1, pict.rows_[py].size() - 2);
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}
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}
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}
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assert(rows_.size() == array.height() * 8);
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assert(rows_[0].size() == array.width() * 8);
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}
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int main(void) {
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PictureArray pictures_;
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std::string line;
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while (std::getline(std::cin, line)) {
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if (line.empty()) {
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continue;
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}
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Picture pic(line, std::cin);
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pictures_.add(std::move(pic));
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}
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auto solution = pictures_.solve();
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std::cout << "Product = " << solution << "\n";
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Picture merged(pictures_);
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auto monster_count = merged.find_monsters();
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std::cout << merged;
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std::cout << "Number of monsters: " << monster_count << "\n";
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std::cout << "Roughness: " << merged.roughness() << "\n";
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return 0;
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}
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