187. repeated dna sequences

All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: “ACGAATTCCG”. When studying DNA, it is sometimes useful to identify repeated sequences within the DNA.

Write a function to find all the 10-letter-long sequences (substrings) that occur more than once in a DNA molecule.

Example:

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Input: s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT"

Output: ["AAAAACCCCC", "CCCCCAAAAA"]

class  {
    public List<String> findRepeatedDnaSequences(String s) {
        
         List<String> list = new ArrayList<>();
        if (s == null || s.length() < 10) return list;
       Map<String, Integer> map = new HashMap<>();
         int startIndex = 0;
         while (startIndex  + 10 <= s.length()) {
             String str = s.substring(startIndex, startIndex + 10);
           if (map.containsKey(str)) {
                 map.put(str, map.get(str) + 1);
          } else {
                map.put(str, 1);
             }
            startIndex++;
        }
        Set<Map.Entry<String, Integer>> entrySet = map.entrySet();
       for (Map.Entry<String, Integer> set: entrySet) {
          String str = set.getKey();
           Integer v = set.getValue();
          if (v >= 2) {
                list.add(str);
           }
        }
        return list;
    }
}

187. repeated dna sequences

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