Cod sursa(job #360617)
Utilizator | Data | 1 noiembrie 2009 11:31:34 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.35 kb |
#include<fstream.h>
#include<math.h>
#define endl '\n'
ifstream fin("ciur.in");
ofstream fout("ciur.out");
char c[2000001];
int n;
int main(){
int i,j,r,nnp=0;
fin>>n;
c[1]=c[0]=1;
r=sqrt((double)n);
for(i=1;i<=r;i++)
if(c[i]==0)
for(j=2;j*i<=n;j++) c[i*j]=1;
for(i=2;i<=n;i++)
if(c[i]==0) nnp++;
fout<<nnp;
return 0;
}