leetcode:Repeated DNA Sequences

class Solution {
public:
   char hash[1024*1024];
    vector findRepeatedDnaSequences(string s) {
        vector res;
        if(s.size()<10)
            return res;
        char convertor[26];
        convertor[0] = 0;
        convertor[2] = 1;
        convertor[6] = 2;
        convertor[19] = 3;
        memset(hash,'0',sizeof(hash));
        for(int i=0;i