84 lines
1.7 KiB
C++
84 lines
1.7 KiB
C++
//
|
|
// Created by Matthew Gretton-Dann on 11/12/2021.
|
|
//
|
|
|
|
#include <iostream>
|
|
#include <map>
|
|
#include <set>
|
|
#include <string>
|
|
#include <vector>
|
|
|
|
using Coord = std::pair<int, int>;
|
|
|
|
struct State
|
|
{
|
|
State(std::vector<std::string> const& initial)
|
|
{
|
|
for (int y = 0; y < initial.size(); ++y) {
|
|
for (int x = 0; x < initial[y].size(); ++x) {
|
|
octopi_.insert({{x, y}, initial[y][x] - '0'});
|
|
}
|
|
}
|
|
}
|
|
|
|
unsigned sparkle()
|
|
{
|
|
std::set<Coord> visited;
|
|
// Start by incrementing every octopus by one.
|
|
for (auto& o : octopi_) {
|
|
(o.second)++;
|
|
}
|
|
|
|
auto just_visited{0};
|
|
do {
|
|
just_visited = visited.size();
|
|
for (auto const& o : octopi_) {
|
|
if (o.second > 9 && !visited.contains(o.first)) {
|
|
visited.insert({o.first});
|
|
for (int x = o.first.first - 1; x < o.first.first + 2; ++x) {
|
|
for (int y = o.first.second - 1; y < o.first.second + 2; ++y) {
|
|
auto it{octopi_.find({x, y})};
|
|
if (it != octopi_.end()) {
|
|
++(it->second);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
} while (just_visited != visited.size());
|
|
|
|
// And reset the energy levels
|
|
for (auto& o : octopi_) {
|
|
if (o.second > 9) {
|
|
o.second = 0;
|
|
}
|
|
}
|
|
|
|
return visited.size();
|
|
}
|
|
|
|
private:
|
|
std::map<Coord, unsigned> octopi_;
|
|
};
|
|
|
|
auto main() -> int
|
|
{
|
|
std::string line;
|
|
std::vector<std::string> lines;
|
|
|
|
while (std::getline(std::cin, line)) {
|
|
lines.push_back(line);
|
|
}
|
|
|
|
State octopi(lines);
|
|
|
|
constexpr unsigned max_steps{100};
|
|
unsigned count{0};
|
|
for (unsigned i = 0; i < max_steps; ++i) {
|
|
count += octopi.sparkle();
|
|
}
|
|
|
|
std::cout << "After " << max_steps << " we have sparkled " << count << " times.\n";
|
|
return 0;
|
|
}
|