如何在std::sub_match中访问正则表达式搜索结果？

#include <iostream>
#include <regex>
#include <string>

int main() {
    std::string input = "Hello, World!";
    std::regex pattern("Hello, (\\w+)!");

    std::smatch matches;
    if (std::regex_search(input, matches, pattern)) {
        std::cout << "Match found!" << std::endl;

        // 访问整个匹配结果
        std::cout << "Full match: " << matches[0] << std::endl;

        // 访问第一个子匹配
        std::cout << "First sub-match: " << matches[1] << std::endl;

        // 使用迭代器遍历所有子匹配
        for (auto it = matches.begin() + 1; it != matches.end(); ++it) {
            std::cout << "Sub-match: " << *it << std::endl;
        }
    } else {
        std::cout << "No match found." << std::endl;
    }

    return 0;
}