LeetCode: Number of Valid Words for Each Puzzle

class Solution {
public:

    int shift[27];

    int Bit(string &str){
        int len = str.size();
        int alph[27];
        for(int i=1;i<=26;i++)
            alph[i] = false;
        for(int i=0;i<len;i++){
            alph[ str[i] - 'a' + 1 ] = true;
        }
        int bit = 0;
        for(int i=1;i<=26;i++){
            if(alph[i])
                bit = bit | shift[i];
        }
        return bit;
    }

    vector<int> findNumOfValidWords(vector<string>& words, vector<string>& puzzles) {

        shift[0] = 1;
        for(int i=1;i<=26;i++)
            shift[i] = shift[i-1] * 2;

        int nw = words.size(), np = puzzles.size();
        int bitp[np + 1];
        unordered_map <int, int> bitw;
        for(int i=0;i<nw;i++){
            bitw[ Bit(words[i]) ] ++;
        }
        for(int i=0;i<np;i++){
            bitp[i] = Bit(puzzles[i]);
        }
        vector <int> ans;
        for(int i=0;i<np;i++){
            int cnt = 0;
            int fln = puzzles[i][0] - 'a' + 1;
            for(auto j: bitw){
                int bw = j.first;
                int c = j.second;
                if((bw & shift[fln]) == shift[fln] and (bitp[i] & bw) == bw)
                    cnt += c;
            }
            ans.push_back(cnt);
        }

        return ans;
    }
};