Cod sursa(job #2768607)

Utilizator BlaugranasEnal Gemaledin Blaugranas Data 11 august 2021 15:12:21
Problema Ciurul lui Eratosthenes Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.34 kb
Raporteaza aceasta sursa 
#include<cstdio>
#include<bitset>
using namespace std;
int n,i,j;
bitset<2000001> p;
int main()
{
    freopen("ciur.in","r",stdin),freopen("ciur.out","w",stdout),scanf("%d",&n);
    for(i=3;i*i<=n;i+=2)
        if(!p[i])
            for(j=i*i;j<=n;j+=2*i)
                p[j]=1;
    printf("%d",(n+1)/2-p.count());
    return 0;
}