repeated_dna_sequence.py

class Solution:
    def findRepeatedDnaSequences(self, s):
        """
        :type s: str
        :rtype: List[str]
        """
        Map = dict()
        for i in range(len(s)-9):
            if s[i:i+10] not in Map.keys():
                Map[s[i:i+10]] = 1
            else:
                Map[s[i:i+10]] += 1
        
        ret = list()
        for key in Map.keys():
            if Map[key] > 1:
                ret.append(key)
        
        return ret
        
        # brute force method is quadratic