class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定,请勿修改,直接返回方法规定的值即可
     *
     * 
     * @param DNA string字符串 1
     * @return string字符串vector
     */
    vector<string> repeatedDNA(string DNA) {
        // write code here
        int len = 10;
        vector<string> ans;
        unordered_map<string, int> map;
        for(int i = 0; i <= DNA.size() - 10; i++) {
            string s = DNA.substr(i, 10);
            map[s]++;
            if(map[s] == 2)
                ans.push_back(s);
        }
        return ans;
    }
};