返回时如何替换结构中姓名和姓氏的小写字母？

#include <iostream>
#include <string>

struct Person {
    std::string firstName;
    std::string lastName;
};

void replaceLowerCase(Person& person) {
    for (char& c : person.firstName) {
        if (std::islower(c)) {
            c = std::toupper(c);
        }
    }
    
    for (char& c : person.lastName) {
        if (std::islower(c)) {
            c = std::toupper(c);
        }
    }
}

int main() {
    Person person;
    person.firstName = "john";
    person.lastName = "doe";
    
    replaceLowerCase(person);
    
    std::cout << "Updated Name: " << person.firstName << " " << person.lastName << std::endl;
    
    return 0;
}