132 lines
2.6 KiB
C++
132 lines
2.6 KiB
C++
#include <algorithm>
|
|
#include <array>
|
|
#include <cassert>
|
|
#include <iostream>
|
|
#include <list>
|
|
#include <map>
|
|
#include <regex>
|
|
#include <set>
|
|
#include <string>
|
|
#include <tuple>
|
|
#include <vector>
|
|
|
|
using Coord = long;
|
|
using Position = std::pair<Coord, Coord>;
|
|
struct State
|
|
{
|
|
bool black_ = false;
|
|
int neighbours_ = 0;
|
|
};
|
|
using Tiles = std::map<Position, State>;
|
|
|
|
struct Tiler
|
|
{
|
|
void flip_tile(std::string const& s)
|
|
{
|
|
Coord x = 0;
|
|
Coord y = 0;
|
|
auto it = s.begin();
|
|
while (it != s.end()) {
|
|
Coord dx = 2;
|
|
if (*it == 's' || *it == 'n') {
|
|
y += (*it == 'n') - (*it == 's');
|
|
++it;
|
|
dx = 1;
|
|
assert(it != s.end());
|
|
}
|
|
|
|
if (*it == 'e') {
|
|
x += dx;
|
|
}
|
|
else if (*it == 'w') {
|
|
x -= dx;
|
|
}
|
|
else {
|
|
assert(false);
|
|
}
|
|
++it;
|
|
}
|
|
|
|
// Insert tile to be flipped - if we fail remove it.
|
|
flip_tile(x, y);
|
|
}
|
|
|
|
Tiler next_state() const
|
|
{
|
|
Tiler next(*this);
|
|
for (auto const& kv : tiles_) {
|
|
if (kv.second.black_ && (kv.second.neighbours_ == 0 || kv.second.neighbours_ > 2)) {
|
|
next.flip_tile(kv.first.first, kv.first.second);
|
|
}
|
|
else if (!kv.second.black_ && kv.second.neighbours_ == 2) {
|
|
next.flip_tile(kv.first.first, kv.first.second);
|
|
}
|
|
}
|
|
|
|
return next;
|
|
}
|
|
|
|
std::size_t black_count() const noexcept
|
|
{
|
|
std::size_t count = 0;
|
|
for (auto const& kv : tiles_) {
|
|
count += kv.second.black_;
|
|
}
|
|
|
|
return count;
|
|
}
|
|
|
|
private:
|
|
void set_neighbours(Coord x, Coord y, int delta)
|
|
{
|
|
set_neighbour(x + 2, y, delta);
|
|
set_neighbour(x + 1, y - 1, delta);
|
|
set_neighbour(x - 1, y - 1, delta);
|
|
set_neighbour(x - 2, y, delta);
|
|
set_neighbour(x - 1, y + 1, delta);
|
|
set_neighbour(x + 1, y + 1, delta);
|
|
}
|
|
|
|
void set_neighbour(Coord x, Coord y, int delta)
|
|
{
|
|
auto [it, success] = tiles_.insert({{x, y}, {false, delta}});
|
|
if (!success) {
|
|
it->second.neighbours_ += delta;
|
|
}
|
|
assert(it->second.neighbours_ >= 0);
|
|
}
|
|
|
|
void flip_tile(Coord x, Coord y)
|
|
{
|
|
auto [it, success] = tiles_.insert({{x, y}, {true, 0}});
|
|
if (!success) {
|
|
it->second.black_ = !it->second.black_;
|
|
}
|
|
if (it->second.black_) {
|
|
set_neighbours(x, y, 1);
|
|
}
|
|
else {
|
|
set_neighbours(x, y, -1);
|
|
}
|
|
}
|
|
|
|
private:
|
|
Tiles tiles_;
|
|
};
|
|
|
|
int main(void)
|
|
{
|
|
Tiler tiler;
|
|
std::string line;
|
|
while (std::getline(std::cin, line)) {
|
|
tiler.flip_tile(line);
|
|
}
|
|
|
|
std::cout << "Day 0: " << tiler.black_count() << "\n";
|
|
for (unsigned i = 1; i < 101; ++i) {
|
|
tiler = tiler.next_state();
|
|
std::cout << "Day " << i << ": " << tiler.black_count() << "\n";
|
|
}
|
|
|
|
return 0;
|
|
} |