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#include <filesystem>
#include <fstream>
#include <iostream>
#include <map>
#include <numeric>
#include <vector>
using namespace std;
namespace {
struct Node {
int weight;
optional<string> parent;
vector<string> children;
};
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;
}
map<string, Node>
read_file(const filesystem::path& filename)
{
ifstream file{ filename };
map<string, Node> data; // name -> (weight, parent)
for ( string line; getline(file, line); ) {
const auto parts = split(line, " ()->,");
const auto& parent = parts.at(0);
data[parent].weight = stoi(parts.at(1));
for ( size_t idx = 2; idx != parts.size(); ++idx ) {
const auto& child = parts.at(idx);
data[child].parent = parent;
data[parent].children.emplace_back(child);
}
}
return data;
}
string
root_node(const map<string, Node>& data)
{
for ( const auto& [name, node]: data ) {
if ( !node.parent ) {
return name;
}
}
throw runtime_error("no root found");
}
void
part1(const map<string, Node>& data)
{
cout << "Part1: " << root_node(data) << '\n';
}
int
calculate_weight(const map<string, Node>& data, const string& name) // NOLINT
{
const auto& node = data.at(name);
if ( node.children.empty() ) {
return node.weight;
}
int total_weight = node.weight;
map<string, int> child_weights;
for ( const auto& child: node.children ) {
auto child_weight = calculate_weight(data, child);
child_weights.emplace(child, child_weight);
total_weight += child_weight;
}
map<int, vector<string>> grouped;
for ( const auto& [child, weight]: child_weights ) {
grouped[weight].emplace_back(child);
}
if ( grouped.size() != 1 ) {
int wrong_weight{};
int correct_weight{};
string wrong_name;
for ( const auto& [weight, names]: grouped ) {
if ( names.size() == 1 ) {
wrong_weight = weight;
wrong_name = names.front();
}
else {
correct_weight = weight;
}
}
const auto& wrong_node = data.at(wrong_name);
auto diff = wrong_weight - correct_weight;
cout << "Part2: " << wrong_node.weight - diff << '\n';
exit(0);
}
return total_weight;
}
void
part2(const map<string, Node>& data)
{
auto node = root_node(data);
calculate_weight(data, node);
}
} // namespace
int
main()
{
auto data = read_file("data/day07.txt");
part1(data);
part2(data);
}
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