Cod sursa(job #1331284)
Utilizator | Data | 31 ianuarie 2015 15:02:37 | |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.49 kb |
#include <iostream>
#include <fstream>
using namespace std;
ifstream in("ciur.in");
ofstream out("ciur.out");
const int m=2000001;
char prim[m];
int main()
{
int i,n,k=0;
in>>n;
for(i=2;i<n;i++)
{
prim[i]=1;
}
for(i=2;i*i<n;i++)
{
if(prim[i]==1)
{
for(int j=i*i;j<n;j=j+i)
prim[j]=0;
}
}
for(i=1;i<=n;i++)
{
if(prim[i]==1)k++;
}
out<<k;
return 0;
}