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#include <cstdlib>
#include <fstream>
#include <iostream>
#include <iterator>
#include <map>
#include <memory>
#include <string>
#include <vector>
using namespace std;
struct Node {
Node* parent = nullptr;
map<string, shared_ptr<Node>> sub;
map<string, long> files;
};
Node
read_file(string_view filename, ostream& debug)
{
Node root;
Node* current = &root;
fstream input{ filename };
string line;
getline(input, line);
while ( input ) {
if ( line.starts_with("$ ") ) {
if ( line == "$ cd /" ) {
debug << "cd root" << endl;
current = &root;
getline(input, line);
}
else if ( line == "$ cd .." ) {
debug << "cd one up" << endl;
current = current->parent;
getline(input, line);
}
else if ( line == "$ ls" ) {
debug << "list dir" << endl;
getline(input, line);
while ( input && !line.starts_with("$ ") ) {
if ( line.starts_with("dir ") ) {
const auto name = line.substr(4);
const auto node = make_shared<Node>();
node->parent = current;
current->sub[name] = node;
debug << "new subdir " << name << endl;
}
else {
const auto pos = line.find(' ');
const auto size = stol(line.substr(0, pos));
const auto name = line.substr(pos + 1);
current->files[name] = size;
debug << "new file " << name << " (" << size << ")" << endl;
}
getline(input, line);
}
}
else if ( line.starts_with("$ cd ") ) {
const auto dirname = line.substr(5);
current = current->sub[dirname].get();
debug << "cd into " << dirname << endl;
getline(input, line);
}
else {
cerr << "error in line: " << line << endl;
exit(EXIT_FAILURE);
}
}
else {
cerr << "error II in line: " << line << endl;
exit(EXIT_FAILURE);
}
}
return root;
}
void
print(const Node& node, const string& indent = "")
{
if ( node.parent == nullptr ) {
cout << indent << "/" << endl;
}
for ( const auto& [name, sub]: node.sub ) {
cout << indent << name << endl;
print(*sub.get(), indent + " ");
}
for ( const auto& [filename, filesize]: node.files ) {
cout << indent << filename << " (" << filesize << ")" << endl;
}
}
long
part1_rec(const Node& node, long& all)
{
long size = 0;
for ( const auto& [name, sub]: node.sub ) {
const auto sub_size = part1_rec(*sub.get(), all);
if ( sub_size <= 100000 ) {
all += sub_size;
}
size += sub_size;
}
for ( const auto& [filename, filesize]: node.files ) {
size += filesize;
}
return size;
}
void
part1(const Node& node)
{
long all = 0;
part1_rec(node, all);
cout << all << endl;
}
long
part2_rec(const Node& node, vector<long>& sizes)
{
long size = 0;
for ( const auto& [name, sub]: node.sub ) {
const auto sub_size = part2_rec(*sub.get(), sizes);
sizes.emplace_back(sub_size);
size += sub_size;
}
for ( const auto& [filename, filesize]: node.files ) {
size += filesize;
}
return size;
}
void
part2(const Node& node)
{
vector<long> sizes;
const auto needed = 30000000 - (70000000 - part2_rec(node, sizes));
vector<long> candidates;
copy_if(begin(sizes), end(sizes), back_inserter(candidates), [&](auto size) {
return size >= needed;
});
sort(begin(candidates), end(candidates));
cout << candidates[0] << endl;
}
int
main()
{
struct NullBuffer : public streambuf {
int overflow(int chr) final { return chr; }
};
NullBuffer nullBuffer;
ostream nullStream(&nullBuffer);
const auto node = read_file("data/day07.txt", nullStream);
part1(node);
part2(node);
}
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