C++ Extract number from the middle of a string

Question

I have a vector containing strings that follow the format of text_number-number

Eg: Example_45-3

Answer 1

This should be more efficient than Ashot Khachatryan's solution. Note the use of '_' and '-' instead of "_" and "-". And also, the starting position of the search for '-'.

inline std::string mid_num_str(const std::string& s) {
    std::string::size_type p  = s.find('_');
    std::string::size_type pp = s.find('-', p + 2); 
    return s.substr(p + 1, pp - p - 1);
}

If you need a number instead of a string, like what Alexandr Lapenkov's solution has done, you may also want to try the following:

inline long mid_num(const std::string& s) {
    return std::strtol(&s[s.find('_') + 1], nullptr, 10);
}