High-Access Employees — C++

// Time:  O(nlogn)
// Space: O(n)

// sort, two pointers, sliding window
class Solution {
public:
    vector<string> findHighAccessEmployees(vector<vector<string>>& access_times) {
        static const int LIMIT_COUNT = 2;
        static const int LIMIT_MINUTE = 60;
    
        const auto& to_minute = [](const auto& s) {
            return stoi(s.substr(0, 2)) * 60 + stoi(s.substr(2));
        };
    
        unordered_map<string, vector<int>> lookup;;
        for (const auto& x : access_times) {
            lookup[x[0]].emplace_back(to_minute(x[1]));
        }
        vector<string> result;
        for (auto& [x, ts] : lookup) {
            sort(begin(ts), end(ts));
            for (int i = 0; i + LIMIT_COUNT < size(ts); ++i) {
                if (!(ts[i] + LIMIT_MINUTE <= ts[i + LIMIT_COUNT])) {
                    result.emplace_back(x);
                    break;
                }
            } 
        }
        return result;
    }
};