432. All O`one Data Structure

class AllOne {
public:
    unordered_map<string,int> count;
    set<pair<int,string>> se;
    AllOne() {
        count.clear();
    }

    void inc(string key) {
        int n = count[key];
        count[key]++;
        se.erase({n,key});
        se.insert({n+1,key});
    }
    void dec(string key) {
        int n = count[key];
        count[key]--;
        se.erase({n,key});
        if(count[key] > 0) se.insert({n-1,key});
    }
    
    string getMaxKey() {
        if(!se.empty()) return se.rbegin()->second;
        return "";
    }
    
    string getMinKey() {
        if(!se.empty()) return se.begin()->second;
        return "";
    }
};

/**
 * Your AllOne object will be instantiated and called as such:
 * AllOne* obj = new AllOne();
 * obj->inc(key);
 * obj->dec(key);
 * string param_3 = obj->getMaxKey();
 * string param_4 = obj->getMinKey();
 */