class Solution {
public:
    vector<string> findRepeatedDnaSequences(string s) {
        vector<string> res;
        unordered_map<string, int> m;
        int n = s.size();
        for(int i = 0; i < n; i++) {
            string tmp = "";
            for(int j = i; j < min(i + 10, n); j++) {
                tmp += s[j];
            }
            if(tmp.size() == 10) {
                m[tmp]++;
            }
        }
        for(unordered_map<string, int>::iterator it = m.begin(); it != m.end(); it++) {
            if(it->second > 1) {
                res.push_back(it->first);
            }
        }
        return res;
    }
};