109 lines
2.4 KiB
C++
109 lines
2.4 KiB
C++
#include <cassert>
|
|
#include <iostream>
|
|
#include <string>
|
|
#include <vector>
|
|
|
|
struct State
|
|
{
|
|
explicit State(std::string const& rules)
|
|
: rules_(rules)
|
|
{
|
|
assert(rules.size() == 512);
|
|
assert(rules[0] == '.' || rules[511] == '.');
|
|
}
|
|
|
|
void add_row(std::string const& row)
|
|
{
|
|
using namespace std::string_literals;
|
|
lights_.push_back(row);
|
|
}
|
|
|
|
auto size() const noexcept -> std::size_t
|
|
{
|
|
std::size_t result{0};
|
|
for (auto const& row : lights_) {
|
|
result += std::count(row.begin(), row.end(), '#');
|
|
}
|
|
return result;
|
|
}
|
|
|
|
auto next() const -> State
|
|
{
|
|
std::ptrdiff_t longest_line(
|
|
std::max_element(lights_.begin(), lights_.end(), [](auto const& l, auto const& r) {
|
|
return l.size() < r.size();
|
|
})->size());
|
|
State result{rules_};
|
|
if (rules_[0] == '#') {
|
|
result.outside_set_ = !outside_set_;
|
|
}
|
|
std::ptrdiff_t row_count(lights_.size());
|
|
for (std::ptrdiff_t y{-1}; y <= row_count; ++y) {
|
|
std::string next_row;
|
|
next_row.reserve(longest_line);
|
|
for (std::ptrdiff_t x{-1}; x <= longest_line; ++x) {
|
|
next_row.push_back(lit(x, y) ? '#' : '.');
|
|
}
|
|
result.add_row(next_row);
|
|
}
|
|
return result;
|
|
}
|
|
|
|
[[nodiscard]] auto lit(std::ptrdiff_t x0, std::ptrdiff_t y0) const noexcept -> bool
|
|
{
|
|
auto num{0};
|
|
for (auto y{y0 - 1}; y < y0 + 2; ++y) {
|
|
for (auto x{x0 - 1}; x < x0 + 2; ++x) {
|
|
num <<= 1;
|
|
num |= bit_set(x, y);
|
|
}
|
|
}
|
|
return rules_[num] == '#';
|
|
}
|
|
|
|
void print(std::ostream& os) const
|
|
{
|
|
for (auto const& row : lights_) {
|
|
os << row << '\n';
|
|
}
|
|
}
|
|
|
|
private:
|
|
auto bit_set(std::ptrdiff_t x, std::ptrdiff_t y) const noexcept -> bool
|
|
{
|
|
if (y < 0 || y >= lights_.size()) {
|
|
return outside_set_;
|
|
}
|
|
if (x < 0 || x >= lights_[y].size()) {
|
|
return outside_set_;
|
|
}
|
|
return lights_[y][x] == '#';
|
|
}
|
|
|
|
std::string rules_;
|
|
std::vector<std::string> lights_;
|
|
bool outside_set_{false};
|
|
};
|
|
|
|
auto main() -> int
|
|
{
|
|
std::string line;
|
|
if (!std::getline(std::cin, line)) {
|
|
std::cerr << "Unable to read rules.\n";
|
|
return 1;
|
|
}
|
|
State state{line};
|
|
std::getline(std::cin, line);
|
|
assert(line.empty());
|
|
while (std::getline(std::cin, line) && !line.empty()) {
|
|
state.add_row(line);
|
|
}
|
|
|
|
constexpr unsigned count{50};
|
|
for (unsigned i{0}; i < count; ++i) {
|
|
state = state.next();
|
|
}
|
|
|
|
std::cout << "Number lit: " << state.size() << '\n';
|
|
}
|