[Leetcode 187, medium] Repeated DNA Sequences

Problem:

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"].

Analysis:

Solutions:

C++:

    vector<string> findRepeatedDnaSequences(string s) {        vector<string> r_set_strings;        if(s.size() < 10)            return r_set_strings;        int codebook[26];        codebook['A' - 'A'] = 0;        codebook['C' - 'A'] = 1;        codebook['G' - 'A'] = 2;        codebook['T' - 'A'] = 3;        bool hash_substr[1024 * 1024];        memset(hash_substr, false, 1024 * 1024);        int size = s.size();        int int_substr = 0;        const int mask = (1<<20) - 1;        for(int i = 0; i < size; ++i) {            int_substr <<= 2;            int_substr = (int_substr & mask) | codebook[s[i] - 'A'];            if(i < 9)                continue;            if(!hash_substr[int_substr])                hash_substr[int_substr] = true;            else if(find(r_set_strings.begin(), r_set_strings.end(), s.substr(i - 9, 10)) == r_set_strings.end())                r_set_strings.push_back(s.substr(i - 9, 10));        }        return r_set_strings;    }

Java:

Python: