Question

I am writing a method whose signature is

bool isValidString(std::string value)

Inside this method I want to search all the characters in value are belongs to a set of characters which is a constant string

const std::string ValidCharacters("abcd")

To perform this search I take one character from value and search in ValidCharacters,if this check fails then it is invalid string is there any other alternative method in STL library to do this check.

Answer 1

Use find_first_not_of():

bool isValidString(const std::string& s) {
    return std::string::npos == s.find_first_not_of("abcd");
}