Cod sursa(job #681670)
Utilizator | Data | 17 februarie 2012 17:08:26 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.31 kb |
#include<iostream>
#include<fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
bool c[2000001];
int main(){
int n,i,j,nr=0;
in>>n;
for(i=2;i*i<=n;i++){
if(!c[i])
for(j=i*i;j<=n;j+=i)
c[j]=true;
}
for(i=2;i<=n;i++){
if(!c[i]) nr++;
}
out<<nr;
return 0;
}