Leetcode OJ : Repeated DNA Sequences hash python solution

Total Accepted: 3790 Total Submissions: 21072

 

 

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.

For example,

Given s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT", Return: ["AAAAACCCCC", "CCCCCAAAAA"].

 

很水的hashtable

class Solution:
    # @param s, a string
    # @return a list of strings
    def findRepeatedDnaSequences(self, s):
        hashset, addedset, retlist = set(), set(), []
        for x in range(len(s)):
            substr = s[x: x + 10]
            if substr in hashset:
                if substr not in addedset:
                    retlist.append(substr)
                    addedset.add(substr)
            else:
                hashset.add(substr)
        return retlist