82 lines
1.8 KiB
C++
82 lines
1.8 KiB
C++
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#include <algorithm>
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#include <cstdint>
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#include <iostream>
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#include <fstream>
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#include <iterator>
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#include <vector>
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#include <map>
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#include <aocpp/Startup.hpp>
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namespace {
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auto Parse(std::istream & in) {
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std::map<std::string, std::string> parents;
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std::string line;
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while (std::getline(in, line)) {
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auto it = line.find(')');
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if (it == std::string::npos) throw std::runtime_error{"bad input entry"};
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parents.insert({line.substr(it+1), line.substr(0, it)});
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}
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return parents;
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}
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auto Path(std::map<std::string, std::string> const& parents, std::string const& start)
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{
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std::vector<std::string> path;
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std::string const* name = &start;
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while (*name != "COM") {
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name = &parents.at(*name);
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path.push_back(*name);
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}
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return path;
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}
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auto Part1(std::map<std::string, std::string> const& parents) {
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std::map<std::string, std::size_t> depths {{"COM", 0}};
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std::size_t part1 {0};
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for (auto & [k, _] : parents) {
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std::string const* cursor = &k;
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std::vector<std::string const*> todo;
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decltype(depths)::iterator it;
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while (depths.end() == (it = depths.find(*cursor))) {
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todo.push_back(cursor);
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cursor = &parents.at(*cursor);
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}
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auto n = it->second;
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for (; !todo.empty(); todo.pop_back()) {
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depths[*todo.back()] = ++n;
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}
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part1 += n;
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}
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return part1;
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}
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auto Part2(std::map<std::string, std::string> const& parents) {
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auto p1 = Path(parents, "SAN");
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auto p2 = Path(parents, "YOU");
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while (p1.back() == p2.back()) {
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p1.pop_back();
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p2.pop_back();
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}
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return p1.size() + p2.size();
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}
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} // namespace
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auto main(int argc, char** argv) -> int {
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auto parents = Parse(aocpp::Startup(argc, argv));
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std::cout << "Part 1: " << Part1(parents) << std::endl;
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std::cout << "Part 2: " << Part2(parents) << std::endl;
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}
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