How can i initialize a set using loop in c++?

Question

I need to know can initialize a set using loop and how?
What should i make in this code?

#include <iostream>
#include <set>
using namespace std;
int main()
{
  set <char>s;
  for (auto it = s.begin(); it != s.end();it++){
      cin >>*it;
  }
  return 0;
}

Answer 1

I'm going to assume you want to loop over all the user input. Note that the simplest way I have shown will ignore whitespace.

#include <iostream>
#include <set>
int main()
{
    std::set<char> s;
    char c; // input from user
    while (std::cin >> c) { // read until end of input
        s.insert(c);
    }

    // do something with s, I guess?
}

This: std:cin >> c will fail when the user finishes their input, which will terminate the loop. I'll repeat myself: std::cin >> skips whitespace . If you want to also read any whitespace characters the user inputs, I can show a way to do that too.

Iterators only let you access items that are already in the std::set (or other container), and in the case of std::set you can't assign to things once they are in there.

Please also note that using namespace std; is widely considered to be bad practice .