inserter.cpp

#include <iostream>
#include <set>
#include <string>
#include <vector>
#include <iterator>
#include <algorithm>

using std::set;
using std::string;
using std::cin;
using std::cout;
using std::endl;
using std::vector;
using std::istream_iterator;
using std::back_inserter;
using std::less;

bool insert_new(const char& c);

int main() {
	cout << "Insert characters, end with CTRL+Z (+ enter)" << endl;
	vector<char> c, v;
	copy_if(istream_iterator<char>(cin),
	     istream_iterator<char>(),
		back_inserter(c),
		[](const char c) {
		return insert_new(c) == true;
	});
	sort(c.begin(), c.end(), less<char>());
	for (auto i : c) {
		cout << i;;
	}
	getchar();
	return 0;
}

bool insert_new(const char& c) {
	static set<char> cc;
	return cc.insert(c).second;
}