题目描述：
方法一：
class Solution:def findRepeatedDnaSequences(self, s: str) -> List[str]:n = 10d = {}for i in range(len(s)-9):if s[i:i+10] in d:d[s[i:i+10]] = Trueelse:d[s[i:i+10]] = Falsereturn [i for i in d if d[i]]
方法二：
class Solution:def findRepeatedDnaSequences(self, s: str) -> List[str]:n = 10d = collections.defaultdict(int)for i in range(len(s)-9):d[s[i:i+10]] += 1return [i for i in d if d[i]>1]
方法三：
class Solution:def findRepeatedDnaSequences(self, s: str) -> List[str]:n=len(s)-9 d=set() ans=set() for i in range(n): if s[i:i+10] not in d: d.add(s[i:i+10]) elif s[i:i+10] not in ans: ans.add(s[i:i+10]) return list(ans)
