Add Binary Strings.cpp

string Solution::addBinary(string A, string B) {
      string r ;
        int s = 0;
    int i = A.size() - 1, j = B.size() - 1;
    while (i >= 0 || j >= 0 || s == 1)
    {
        s += ((i >= 0)? A[i] - '0': 0);
        s += ((j >= 0)? B[j] - '0': 0);
        r = char(s % 2 + '0') + r;
        s /= 2;
        i--; j--;
    }
    return r;
}