stringstream input

ss.cpp

#include <iostream>
#include <sstream>
using namespace std;

int main() {
        stringstream ss;
        ss << "5 10 20";
        cin.rdbuf(ss.rdbuf());
        int n;
        while(cin >> n) {
                cout << "n: " << n << endl;
        }
        return 0;
}