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#include <algorithm>
#include <filesystem>
#include <fstream>
#include <iostream>
#include <string>
using namespace std;
namespace {
string
readFile(const filesystem::path& filename)
{
ifstream file{ filename };
string line;
getline(file, line);
return line;
}
void
solve(string line, size_t lines)
{
long count = 0;
while ( lines-- > 0 ) {
string current_line = "." + line + ".";
string new_line;
for ( size_t i = 1; i < current_line.size() - 1; ++i ) {
auto next_chr = '.';
const auto left = current_line[i - 1];
const auto middle = current_line[i];
const auto right = current_line[i + 1];
if ( left == '^' && middle == '^' && right == '.' ) {
next_chr = '^';
}
else if ( left == '.' && middle == '^' && right == '^' ) {
next_chr = '^';
}
else if ( left == '^' && middle == '.' && right == '.' ) {
next_chr = '^';
}
else if ( left == '.' && middle == '.' && right == '^' ) {
next_chr = '^';
}
new_line += next_chr;
}
count += ranges::count(line, '.');
line = std::move(new_line);
}
cout << count << '\n';
}
void
part1(const string& line)
{
solve(line, 40);
}
void
part2(const string& line)
{
solve(line, 400000);
}
} // namespace
int
main()
{
auto line = readFile("data/day18.txt");
part1(line);
part2(line);
}
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