tree.cc

struct Directory {
    // Required for "$ cd ..".
    Directory *parent = nullptr;
    // Required for "$ cd subdirectory".
    std::unordered_map<std::string, Directory*> subdirs;
    // Information about files.
    std::unordered_map<std::string, size_t> files;
};

struct Tree {
    // Directory root.
    Directory root;
    // Storage for all Directories.
    std::vector<std::unique_ptr<Directory>> storage;
};