LeetCode: Repeated DNA Sequences

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"].

class Solution {
public:
    vector findRepeatedDnaSequences(string s) {
        map m_map;
        map convert;
        int cur = 0;
        convert['A'] = 0;
        convert['C'] = 1;
        convert['G'] = 2;
        convert['T'] = 3;
        vector result;
        if(s.size() < 10)
            return result;
        for(int i = 0; i < s.size(); i++)
        {
            cur = (cur << 2 | convert[s[i]]) & 0xFFFFF;
            if(m_map[cur] == 1 && i >= 9)
                result.push_back(s.substr(i-9, 10));
            if(i >= 9)
                m_map[cur]++;
        }
        return result;
    }
};