Cod sursa(job #929428)
Utilizator | Horea Stefan AeroH | Data | 27 martie 2013 00:31:47 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 90 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.47 kb |
#include <cstdio>
#include <vector>
#include <algorithm>
using namespace std;
FILE*fin=fopen("ciur.in","r");
FILE*fout=fopen("ciur.out","w");
int i,j,k,m,l,n,a,rasp;
//vector <int> v;
char v[5000000];
int main()
{
fscanf(fin,"%d",&n);
for (i=1;(i<<1)+1<n;i++)
if (v[i]==0)
for(j=(i<<2)-i+1;(j<<1)+1<n;j+=(i<<1)+1)
v[j]=1;
for (i=1;(i<<1)+1<=n;i++)
if (v[i]==0)
++rasp;
++rasp;
fprintf(fout,"%d\n",rasp);
return 0;
}