Find Duplicate File in System — C++

// Time:  O(n * l), l is the average length of file content
// Space: O(n * l)

class Solution {
public:
    vector<vector<string>> findDuplicate(vector<string>& paths) {
        unordered_map<string, vector<string>> files;
        for (const auto& path : paths) {
    	    stringstream ss(path);
    	    string root;
    	    string s;
    	    getline(ss, root, ' ');
    	    while (getline(ss, s, ' ')) {
    		    auto fileName = root + '/' + s.substr(0, s.find('('));
    		    auto fileContent = s.substr(s.find('(') + 1, s.find(')') - s.find('(') - 1);
    		    files[fileContent].emplace_back(fileName);
    	    }
        }
    
        vector<vector<string>> result;
        for (const auto& file : files) {
    	    if (file.second.size() > 1) {
    		    result.emplace_back(file.second);
    	    }
        }
        return result;
    }
};