Chapter 6: exercise 4

#include <iostream>
#include <vector>
#include <string>

class Name_value {
public:
    Name_value(std::string name, int age) : name_(name), age_(age) {
    }
    std::string name_;
    int age_;
};

int main() {
    std::vector<Name_value> person;
    Name_value inf("Noname", 25);
    bool isNoNameEntered = false;

    do {
        std::cin >> inf.name_;
        if (inf.name_ == "NoName") {
            isNoNameEntered = true;
            break;
        }
        std::cin >> inf.age_;

        bool duplicate_name = false;
        for (const auto& l : person) {
            if (inf.name_ == l.name_) {
                duplicate_name = true;
                break;
            }
        }
        if (duplicate_name) {
            std::cout << "Error: Name already exists!" << std::endl;
        }
        else {
            person.push_back(inf);
        }
    } while (true);

    if (isNoNameEntered) {
        for (const auto& info : person) {
            std::cout << "Name: " << info.name_ << " Age: " << info.age_ << std::endl;
        }
    }
    else {
        std::cout << "NoName entered before printing the result." << std::endl;
    }

    return 0;
}