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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.

第一种方法，像切猪肉那样，将s分成两段，然后比较，可惜TLE了

class Solution(object):    def findRepeatedDnaSequences(self,s):        list_=list(s)        ans=[]        while  len(list_)>10:            sub_string="".join([list_[i] for i in range(10)])            sub_string2=s[s.find(sub_string)+len(sub_string):]            if sub_string in sub_string2 and sub_string not in ans:                ans.append(sub_string)            list_.remove(list_[0])        return ans

第二种方法，存在字典中，如果在字典中出现且在ans中未曾录入的，则ans.append()，注意细节，range(len(s)-9)而不是-10

class Solution(object):    def findRepeatedDnaSequences(self,s):        doc={}        ans=[]        if len(s)<=10:            return ans        for i in range(len(s)-9):            temp=s[i:i+10]            if temp not in doc:                doc.setdefault(temp,None)            else:                if temp not in ans:                    ans.append(temp)        return ans

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