如何在C++中更改存储在字符串中的文件扩展名？

#include<iostream>
#include<string>

std::string change_file_extension(const std::string& filename, const std::string& new_extension) {
    size_t dot_pos = filename.rfind('.');
    if (dot_pos != std::string::npos) {
        return filename.substr(0, dot_pos + 1) + new_extension;
    } else {
        return filename + "." + new_extension;
    }
}

int main() {
    std::string filename = "example.txt";
    std::string new_extension = "csv";
    std::string new_filename = change_file_extension(filename, new_extension);
    std::cout << "New filename: "<< new_filename<< std::endl;
    return 0;
}