Cod sursa(job #1662424)
Utilizator | Ana Vasiliu anav23 | Data | 24 martie 2016 19:15:02 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.59 kb |
#include <iostream>
#include <fstream>
#include <bitset>
using namespace std;
bitset<2000002> prime;
int ciur(int n) {
prime.set();
for(int i=2;i*i<=n;i++) {
if(prime[i]) {
int k=2;
while(i*k<=n) {
prime[i*k]=false;
k++;
}
}
}
int n_prime=0;
for(int i=2;i<=n;i++)
if(prime[i])
n_prime++;
return n_prime;
}
int main()
{
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n;
fin>>n;
fout<<ciur(n);
return 0;
}