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#include <filesystem>
#include <fstream>
#include <iostream>
#include <set>
#include <vector>
using namespace std;
namespace {
vector<tuple<long, long>>
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
vector<tuple<long, long>> data;
long lhs = 0;
long rhs = 0;
char sep = 0;
while ( file >> lhs >> sep >> rhs ) {
data.emplace_back(lhs, rhs);
}
return data;
}
long
strongest(const vector<tuple<long, long>>& data, long current = 0, const set<size_t>& used = {})
{
long best_strength = 0;
for ( size_t i = 0; i != data.size(); ++i ) {
if ( used.contains(i) ) {
continue;
}
auto [lhs, rhs] = data.at(i);
if ( lhs == current || rhs == current ) {
auto next_port = (lhs == current) ? rhs : lhs;
auto new_used{ used };
new_used.emplace(i);
auto strength = lhs + rhs + strongest(data, next_port, new_used);
best_strength = max(best_strength, strength);
}
}
return best_strength;
}
tuple<long, size_t>
strongest_and_longest(const vector<tuple<long, long>>& data, long current = 0, const set<size_t>& used = {})
{
long best_strength = 0;
size_t best_length = 0;
for ( size_t i = 0; i != data.size(); ++i ) {
if ( used.contains(i) ) {
continue;
}
auto [lhs, rhs] = data.at(i);
if ( lhs == current || rhs == current ) {
auto next_port = (lhs == current) ? rhs : lhs;
auto new_used{ used };
new_used.emplace(i);
auto [sub_strength, sub_length] = strongest_and_longest(data, next_port, new_used);
auto total_strength = sub_strength + lhs + rhs;
auto total_length = sub_length + 1;
if ( total_length > best_length || (total_length == best_length && total_strength > best_strength) ) {
best_strength = total_strength;
best_length = total_length;
}
}
}
return make_tuple(best_strength, best_length);
}
void
part1(const vector<tuple<long, long>>& data)
{
cout << "Part1: " << strongest(data) << '\n';
}
void
part2(const vector<tuple<long, long>>& data)
{
auto [strength, length] = strongest_and_longest(data);
cout << "Part2: " << strength << '\n';
}
} // namespace
int
main()
{
auto data = read_file("data/day24.txt");
part1(data);
part2(data);
}
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