Cod sursa(job #1542209)
Utilizator | leustean vlad skitnik | Data | 5 decembrie 2015 09:55:32 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.48 kb |
#include <fstream>
#define N 2000001
using namespace std;
ifstream cin("ciur.in");
ofstream cout("ciur.out");
bool a[N];
int prim[N];
int n;
int main()
{
cin>>n;
for (int i=4; i<=n; i+=2) a[i]=1;
for (int i=3; i*i<=n; i+=2)
if (a[i]==0)
for (int j=i*i; j<=n; j=j+2*i)
a[j]=1;
int k=0;
int ct=1;
prim [++k]=2;
for (int i=3; i<=n; i+=2)
if (a[i]==0) {prim[++k]=i; ct++;}
cout<<ct<<" ";
return 0;
}