Leetcode161: 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"].

用Map的话超内存了，改用bitsmap，因为只有4个字母，所以只要用两位就可以做为一个字母的编码，10个字母就是20位，所以创建一个2^20大小的数组就可以解决问题了。

class Solution {
public:
    int chartoint(char a)
    {
        if(a == 'A') return 0;
        if(a == 'C') return 1;
        if(a == 'G') return 2;
        if(a == 'T') return 3;
    }
    vector findRepeatedDnaSequences(string s) {
        vector res;
        set temp;
        string str;
        if(s.size()<10)
            return res;
        unsigned int val = 0;
        for(int i = 0; i < 9; i++)
        {
            val <<= 2;
            val |= chartoint(s[i]);
        }
        int map[1024*1024] = {0};
        for(int i = 9; i < s.size(); i++)
        {
            val <<= 14;
            val >>= 12;
            val |= chartoint(s[i]);
            map[val]++;
            if(map[val] > 1)
            {
                str = s.substr(i-9, 10);
                temp.insert(str);
            }
        }
        for(set::iterator i = temp.begin(); i != temp.end(); ++i)
        {
            res.push_back(*i);
        }
        return res;
    }
};