题解解解解解解解解解解解解解解解解解解解

题解解解解解解解解解解解解解解解解

#include <iostream>
#include <vector>
using namespace std;
vector<int> findPrimes(int N) {
vector<bool> isPrime(N + 1, true);
isPrime[0] = isPrime[1] = false;

for (int p = 2; p * p <= N; p++) {
    if (isPrime[p]) {
        for (int i = p * p; i <= N; i += p) {
            isPrime[i] = false;
        }
    }
}
vector<int> primes;
for (int i = 2; i <= N; i++) {
    if (isPrime[i]) {
        primes.push_back(i);
    }
}
return primes;

}

int main() {
int N;
cin >> N;
vector<int> primes = findPrimes(N);
for (int prime : primes) {
cout << prime << " ";
}
cout << endl;
return 0;
}