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class Solution {
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 public:
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  vector<string> findRepeatedDnaSequences(string s) {
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    unordered_map<string, int> freq;
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    int start = 0, end = 9;
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    while (end < s.size()) {
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      bool flag = true;
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      for (int i = start; i <= end; i++) {
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        if (s[i] == 'A' or s[i] == 'C' or s[i] == 'G' or s[i] == 'T')
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          continue;
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        else {
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          flag = false;
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          break;
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        }
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      }
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      if (flag) {
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        string temp = s.substr(start, 10);
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        freq[temp]++;
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      }
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      start++;
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      end++;
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    }
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    vector<string> ans;
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    for (auto it : freq) {
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      if (it.second >= 2) ans.push_back(it.first);
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    }
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    return ans;
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  }
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};