vector<string> in a struct doesn't work properly - c++

Question

I declared a vector<string> and I cannot even compile it. I tried many ways but none of them worked.
I'm trying to write out the x.surname.push_back(word)[i] but it's definetly written wrongly and I have no idea how to write it properly and make it possible to compile.
#include <cstring>
#include <iostream>
#include <vector>
using namespace std;
int main() {
int number, i = 0;
string word;
struct donators {
vector<string> surname;
vector<int> amount;
} x;
cout << "How many donators do you want to register? " << endl;
cin >> number;
for (i = 0; i < number; i++) {
cout << "Surname: ";
cin >> word;
x.surname.push_back(word)[i];
cout << "Amount: ";
x.amount.push_back(i);
cin >> x.amount[i];
}
cout << "OUR GORGEUS DONATORS: " << endl;
for (i = 0; i < number; i++) {
if (x.amount[i] >= 10000) {
cout << "Surname: " << x.surname(word)[i];
cout << "Amount: " << x.amount[i] << endl;
}
else if (x.amount[i] < 10000) {
cout << "Lack of surnames!" << endl;
}
}
cout << "OUR CASUAL DONATORS: " << endl;
for (i = 0; i < number; i++) {
if (x.amount[i] < 10000) {
cout << "Surname: " << x.surname(word)[i];
cout << "Amount: " << x.amount[i] << endl;
} else if (x.amount[i] >= 10000) {
cout << "Lack of surnames!" << endl;
}
}
return 0;
}
And one more thing. How to make sentence "Lack of surnames!" to be written out once? In some cases, it is written out twice or more times what is redundant.

Answer 1

You are putting [i] at seemingly random places in your code. Such as in x.surname.push_back(word)[i];. Don't add things like this to your code if you're unsure about what they're doing.
The x.surname(word)[i] construct are also wrong. What's x.surname(word) supposed to be? This syntax is for function calls. surname, however, is not a function. It's a std::vector<std::string>. Just put x.surname[i] instead.
And one more thing. How to make sentence "Lack of surnames!" to be
written out once? In some cases, it is written out twice or more times
what is redundant.
That's because you write it for every donor that doesn't fit the criterion. Instead, keep track if any donor fits the criterion and only print it when none ends up fitting. You can do it like this:
bool HasGorgeousDonators = false;
And then in the loop:
if (x.amount[i] >= 10000)
{
cout << "Surname: " << x.surname[i];
cout << "Amount: " << x.amount[i] << endl;
HasGorgeousDonators = true;
}
And after the loop:
if (!HasGorgeousDonators)
cout << "Lack of surnames!" << endl;
Likewise for the other loop. Also, please consider the following Q&A:
Why is "using namespace std;" considered bad practice?

Answer 2

It seems like you are writing C with some C++ help functions. However C++ is a different language. Sure, it supports some C structures, but there's so much more.
Take a look at some of my suggestions for implementation and compare it to your code:
#include <string>
#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>
template<typename T>
T ReadCin(std::string_view const& sv = "") {
T retVal;
if (!sv.empty()) std::cout << sv;
std::cin >> retVal;
return retVal;
}
class Donator {
private:
std::string surname{};
int amount{};
public:
constexpr bool IsGenerous() const noexcept { return amount >= 10000; }
void Read() noexcept {
surname = ReadCin<decltype(surname)>("Surname: ");
amount = ReadCin<decltype(amount)>("Amount: ");
}
friend std::ostream& operator<<(std::ostream& out, Donator const& donator) noexcept {
out << "Surname: " << donator.surname << ", " << "Amount: " << donator.amount;
return out;
}
};
int main() {
std::vector<Donator> donators(ReadCin<int>("How many donators do you want to register?\n"));
for (auto& donator : donators) donator.Read();
std::cout << "OUR GENEROUS DONATORS:\n";
std::copy_if(std::cbegin(donators), std::cend(donators), std::ostream_iterator<Donator>(std::cout, "\n"),
[](Donator const& donator) { return donator.IsGenerous(); });
std::cout << "OUR CASUAL DONATORS:\n";
for (auto const& donator : donators) if (!donator.IsGenerous()) std::cout << donator << '\n'; //alternative
}
I tried to include some of the possibilities using C++. I would really advise you to get a good book on C++.