Cod sursa(job #2574166)
Utilizator | Sebastian Cojocaru Sebaschan | Data | 5 martie 2020 20:41:31 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva educationala | Marime | 0.49 kb |
#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("ciur.in");
ofstream fout("ciur.out");
int n, nr = 0;
char prim[2000001];
int main() {
fin>>n;
for(int i = 2; i <= n; i++)
prim[i] = 1;
for(int i = 2; i*i <= n; i++) {
if(prim[i]) {
for(int j = 2; j <= n/i; j++)
prim[i*j] = 0;
}
}
for(int i = 1; i <= n; i++)
if(prim[i])
nr++;
fout<<nr;
return 0;
}