105 lines
2.5 KiB
C++
105 lines
2.5 KiB
C++
#include <cassert>
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#include <cctype>
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#include <climits>
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#include <functional>
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#include <iostream>
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#include <map>
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#include <numeric>
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#include <regex>
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#include <set>
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#include <string>
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#include <variant>
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struct ConwayState
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{
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ConwayState(std::size_t width, std::string const& s) : width_(width), state_(width_ * width_, 0)
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{
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assert(s.size() == width_ * width_);
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for (std::size_t i = 0; i < state_.size(); ++i) {
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if (s[i] == '#') {
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flip(i);
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}
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}
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}
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ConwayState next_state() const
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{
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ConwayState next(*this);
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for (std::size_t i = 0; i < state_.size(); ++i) {
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if (state_[i] == (2 | active_) || state_[i] == (3 | active_)) {
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continue;
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}
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if (state_[i] == 3 || (state_[i] & active_) != 0) {
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next.flip(i);
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}
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}
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return next;
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}
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std::size_t num_active() const
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{
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return std::accumulate(
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state_.begin(), state_.end(), std::size_t(0),
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[](std::size_t current, unsigned char info) { return current + ((info & active_) != 0); });
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}
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private:
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void flip(std::size_t idx)
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{
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state_[idx] = state_[idx] ^ active_;
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int delta = ((state_[idx] & active_) == active_) ? 1 : -1;
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std::size_t row = idx / width_;
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std::size_t col = idx % width_;
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for (std::size_t r = std::max(std::size_t(1), row) - 1; r < std::min(width_, row + 2); ++r) {
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for (std::size_t c = std::max(std::size_t(1), col) - 1; c < std::min(width_, col + 2); ++c) {
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if (r == row && c == col) {
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continue;
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}
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state_[r * width_ + c] = state_[r * width_ + c] + delta;
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}
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}
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}
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std::size_t width_;
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std::vector<unsigned char> state_;
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static constexpr unsigned char active_ = 0x80;
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friend std::ostream& operator<<(std::ostream& os, ConwayState const& state);
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};
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std::ostream& operator<<(std::ostream& os, ConwayState const& state)
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{
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std::size_t c = 0;
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for (auto s : state.state_) {
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os << (s & ConwayState::active_ ? '#' : '.');
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os << (s & ~ConwayState::active_);
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++c;
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if (c == state.width_) {
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os << '\n';
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c = 0;
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}
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}
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return os;
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}
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int main(int argc, char** argv)
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{
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std::string line;
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std::size_t width = 0;
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std::string init;
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while (std::getline(std::cin, line)) {
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if (width == 0) {
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width = line.size();
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}
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assert(width == line.size());
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init += line;
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}
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ConwayState conway(width, init);
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for (unsigned i = 0; i < 100; ++i) {
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conway = conway.next_state();
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}
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std::cout << "Solution: " << conway.num_active() << "\n";
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return 0;
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} |