Master Competitive Programming

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

// Sieve of Eratosthenes
vector<int> sieve(int n) {
    vector<bool> is_prime(n + 1, true);
    vector<int> primes;
    
    is_prime[0] = is_prime[1] = false;
    
    for(int i = 2; i <= n; i++) {
        if(is_prime[i]) {
            primes.push_back(i);
            for(int j = i * i; j <= n; j += i)
                is_prime[j] = false;
        }
    }
    return primes;
}

int main() {
    int n;
    cin >> n;
    
    auto primes = sieve(n);
    
    for(int p : primes)
        cout << p << " ";
    
    return 0;
}