The International Standard Book Number (ISBN) is a unique numeric identifier for books. Currently, a 13-digit format is used. However, for this problem, you are to validate the former format that used 10 digits. The last of the 10 digits is a checksum. This digit is chosen so that the sum of all the ten digits, each multiplied by its (integer) weight, descending from 10 to 1, is a multiple of 11.
The validate_isbn_10 function, shown as follows, takes an ISBN as a string, and returns true if the length of the string is 10, all ten elements are digits, and the sum of all digits multiplied by their weight (or position) is a multiple of 11:
bool validate_isbn_10(std::string_view isbn){ auto valid = false; if (isbn.size() ...
