#include #include #include #include #include #include #include #include #include #include namespace { using Grid = std::array, 128>; auto MakeRows(std::string input) -> Grid { Grid rows; input += "-"; for (int i = 0; i < 128; i++) { rows[i] = knothash::hash(input + std::to_string(i)); } return rows; } auto CountBits(Grid const& grid) -> std::size_t { std::size_t bits = 0; for (auto const& row : grid) { for (auto const x : row) { bits += std::popcount(x); } } return bits; } auto Connect(std::vector & leaders, std::uint16_t who, std::uint16_t leader) { auto who_ = leaders[who]; if (who_ == std::uint16_t(-1)) { return; } // there wasn't a node here, abort for (;;) { leaders[who] = leader; if (who_ == who) { return; } who = who_; who_ = leaders[who]; } } auto CountComponents(Grid const& grid) -> std::uint16_t { std::vector leaders(128 * 128); // Visit all pairs of neighbors linking them if both are set for (std::uint16_t r = 0; r < 128; r++) { bool prev = false; for (std::uint16_t c = 0; c < 128; c++) { std::uint16_t me = r*128+c; // first time we've visited this node, if it's in the graph it's a leader! if (grid[r][c/8] & (1<<(7-(c%8)))) { leaders[me] = me; // If previous cell in row is a node, link it to me immediately // It will have just been set as its own group leader. if (prev) { leaders[me-1] = me; } // Connect up's leader _after_ updating left's leader in case they were connected if (0 < r) { Connect(leaders, me - 128, me); } prev = true; } else { prev = false; leaders[me] = -1; } } } // count component leaders std::uint16_t n = 0; for (std::size_t i = 0; i < leaders.size(); i++) { if (leaders[i] == i) { n++; } } return n; } } // namespace TEST_SUITE("2017-14 examples") { TEST_CASE("flqrgnkx") { auto rows = MakeRows("flqrgnkx"); CHECK(CountBits(rows) == 8108); CHECK(CountComponents(rows) == 1242); } } auto Main(std::istream & in, std::ostream & out) -> void { std::string input; std::getline(in, input); auto const rows {MakeRows(std::move(input))}; out << "Part 1: " << CountBits(rows) << std::endl; out << "Part 2: " << CountComponents(rows) << std::endl; }