299

class Solution {
public:
    // only contains digits
    string getHint(string secret, string guess) {
        int aCnt = 0;
        int bCnt = 0;
        vector<int> sVec(10, 0); // 0 ~ 9 for secret
        vector<int> gVec(10, 0); // 0 ~ 9 for guess
        for (int i = 0; i < secret.size(); ++i){
            char c1 = secret[i]; char c2 = guess[i];
            if(c1 == c2)
                ++aCnt;
            else{
                ++sVec[c1-'0'];
                ++gVec[c2-'0'];
            }
        }
        // count b
        for (int i = 0; i < 10; ++i)
            bCnt += min(sVec[i], gVec[i]);
        return to_string(aCnt) + 'A' + to_string(bCnt) + 'B';
    }
};