187. repeated dna sequences

class  {
public:
vector<string> findRepeatedDnaSequences(string s) {
    string temp;
    set<string> set_all,set_result;
    vector<string> a;
    if(s==""||s.length()<10)return a;
    for(int i=0;i<s.length()-9;i++){
        
        temp=s.substr(i,10);
        if(set_all.find(temp)!=set_all.end()){
            if(set_result.find(temp)==set_result.end()){
                set_result.insert(temp);
                a.push_back(temp);
                
            }
        }
        set_all.insert(temp);
    }
    return a;
}

};