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#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <string>
#include <vector>
using namespace std;
namespace {
vector<string>
split(const string& line, const string& delimiters)
{
vector<string> result;
size_t start = 0;
size_t end = 0;
while ( (end = line.find_first_of(delimiters, start)) != string::npos ) {
if ( end != start ) {
result.emplace_back(line.substr(start, end - start));
}
start = end + 1;
}
if ( start != line.size() ) {
result.emplace_back(line.substr(start));
}
return result;
}
vector<string>
rotate90(const vector<string>& input)
{
if ( input.empty() ) {
return {};
}
const auto rows = input.size();
const auto cols = input[0].size();
vector<string> rotated(cols, string(rows, ' '));
for ( size_t row = 0; row != rows; ++row ) {
for ( size_t col = 0; col != cols; ++col ) {
rotated[col][rows - 1 - row] = input[row][col];
}
}
return rotated;
}
vector<string>
flip(const vector<string>& input)
{
vector<string> result = input;
// oder: ranges::reverse(result);
for ( auto& row: result ) {
ranges::reverse(row);
}
return result;
}
vector<vector<string>>
generate_variants(vector<string> pattern)
{
vector<vector<string>> variants;
for ( int flip_count = 0; flip_count < 2; ++flip_count ) {
for ( int round = 0; round < 4; ++round ) {
variants.push_back(pattern);
pattern = rotate90(pattern);
}
pattern = flip(pattern);
}
return variants;
}
map<vector<string>, vector<string>>
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
map<vector<string>, vector<string>> data;
for ( string line; getline(file, line); ) {
auto parts = split(line, " ");
auto lhs = split(parts.at(0), "/");
auto rhs = split(parts.at(2), "/");
for ( const auto& variant: generate_variants(lhs) ) {
data[variant] = rhs;
}
}
return data;
}
vector<string>
enhance(const vector<string>& image, const map<vector<string>, vector<string>>& rules)
{
const auto size = image.size();
const auto block_size = (size % 2 == 0) ? 2U : 3U;
const auto new_block_size = block_size + 1;
const auto blocks_per_row = size / block_size;
const auto new_size = blocks_per_row * new_block_size;
vector<string> new_image(new_size, string(new_size, '.'));
// Für jeden Block...
for ( size_t block_row = 0; block_row != blocks_per_row; ++block_row ) {
for ( size_t block_col = 0; block_col != blocks_per_row; ++block_col ) {
// ...Extrahiere den Block als vector<string>
vector<string> block;
block.reserve(block_size);
for ( size_t row = 0; row != block_size; ++row ) {
block.push_back(image[(block_row * block_size) + row].substr(block_col * block_size, block_size));
}
const auto& new_block = rules.at(block);
// Füge neuen Block ins Bild ein
for ( size_t row = 0; row != new_block_size; ++row ) {
for ( size_t col = 0; col != new_block_size; ++col ) {
new_image[(block_row * new_block_size) + row][(block_col * new_block_size) + col] = new_block[row][col];
}
}
}
}
return new_image;
}
int
count(const vector<string>& image)
{
int count = 0;
for ( const auto& row: image ) {
for ( char chr: row ) {
if ( chr == '#' ) {
++count;
}
}
}
return count;
}
int
solve(const map<vector<string>, vector<string>>& rules, size_t iterations)
{
vector<string> image = { ".#.", "..#", "###" };
while ( iterations-- > 0 ) {
image = enhance(image, rules);
}
return count(image);
}
void
part1(const map<vector<string>, vector<string>>& rules)
{
cout << "Part1: " << solve(rules, 5) << '\n';
}
void
part2(const map<vector<string>, vector<string>>& rules)
{
cout << "Part2: " << solve(rules, 18) << '\n';
}
} // namespace
int
main()
{
auto rules = read_file("data/day21.txt");
part1(rules);
part2(rules);
}
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