查找std::string中存储的主机名是ip地址还是C++中的完全限定域名地址

#include <iostream>
#include <regex>

bool isIPAddress(const std::string& str) {
    std::regex ipRegex(R"(\b(?:\d{1,3}\.){3}\d{1,3}\b)");
    return std::regex_match(str, ipRegex);
}

int main() {
    std::string input;
    std::cout << "Enter a string: ";
    std::cin >> input;

    if (isIPAddress(input)) {
        std::cout << "The string is an IP address." << std::endl;
    } else {
        std::cout << "The string is not an IP address." << std::endl;
    }

    return 0;
}