Cod sursa(job #1011765)
Utilizator | Data | 17 octombrie 2013 14:16:03 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.5 kb |
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
FILE *fin=fopen("ciur.in","r"),*fout=fopen("ciur.out","w");
int n,i,f,s,j;
bool v[2000001]={0};
fscanf(fin,"%d",&n);
f=(int)sqrt((float)n);
v[0]=v[1]=1;
for (i=2;i<=f;++i)
if (!v[i])
for (j=i*i;j<=n;j+=i)
v[j]=1;
s=0;
for (i=2;i<=n;++i)
if (!v[i])
++s;
fprintf(fout,"%d\n",s);
fclose(fin);
fclose(fout);
return 0;
}