Cod sursa(job #2752793)
Utilizator | Data | 19 mai 2021 17:42:37 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.42 kb |
#include <fstream>
using namespace std;
bool v[1999999];
int main() {
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n;
fin >> n;
int cnt_prime_numbers = 1;
for (int i = 3; i * i <= n; i += 2) {
int k = 3;
while (i * k <= n) {
v[i * k] = true;
k += 2;
}
}
for (int i = 3; i <= n; i += 2) {
if (!v[i]) {
++cnt_prime_numbers;
}
}
fout << cnt_prime_numbers;
return 0;
}