Cod sursa(job #2607188)

Utilizator Gliumarin negai Gliu Data 29 aprilie 2020 14:35:28
Problema Ciurul lui Eratosthenes Scor 30
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.33 kb
Raporteaza aceasta sursa 
#include <iostream>
#include <fstream>

using namespace std;

ifstream in("ciur.in");
ofstream out("ciur.out");

int const nmax=2000005;
int n,pr=1;
bool a[nmax];
int main(){

in >>n;

for(int i=3;i<=n;i=i+2){
	if(!a[i]){
		pr++;
	for(int j=i*i;j<=n;j+=i<<1){
	if(j % i==0){
		a[j]=1;
	}
}
}
}
out << pr;
}