187. Repeated DNA Sequences Leetcode Python

hyperbolechi

于 2015-03-16 11:21:30 发布

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分类专栏： leetcode 文章标签： python leetcode

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本文介绍了一种使用哈希表在O(n)时间内查找DNA分子中重复出现的10字母长序列的方法。通过实例展示了如何利用该算法从输入字符串中找出所有重复的子串。

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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.

For example,

Given s = "AAAAACCCCCAAAAACCCCCCAAAAAGGGTTT",

Return:
["AAAAACCCCC", "CCCCCAAAAA"].

this Problem can be solve with O(n) time and O(n) space with hashing

class Solution:
    # @param s, a string
    # @return a list of strings
    def findRepeatedDnaSequences(self, s):
        dict={}
        for i in range(len(s)-9):
            key=s[i:i+10]
            if key not in dict:
                dict[key]=1
            else:
                dict[key]+=1
        res=[]
        for elem in dict:
            if dict[elem]>1:
                res.append(elem)
        return res