Cod sursa(job #1013640)
Utilizator | Bogdan Mucenic mucenic_b101 | Data | 21 octombrie 2013 14:35:43 |
---|---|---|---|
Problema | Ciurul lui Eratosthenes | Scor | 100 |
Compilator | cpp | Status | done |
Runda | Arhiva educationala | Marime | 0.64 kb |
#include<stdio.h>
#include<math.h>
#include<iostream>
using namespace std;
#define MAXN 2000001
bool ciur[MAXN];
int main () {
FILE *f,*g;
f=fopen("ciur.in","r");
g=fopen("ciur.out","w");
int n, i, j,nr;
fscanf(f,"%d",&n);
int p = sqrt(n);
for( int i = 3; i <= p; i= i + 2) {
//cout<<i<<" ";
for(j= i * i ; j <= n; j = j + 2 * i) {
// cout<<j<<endl;
ciur[j]=1;
}
}
nr=1;
for(i=3; i<=n; i += 2)
if(ciur[i]==0)
nr++;
fprintf(g,"%d\n",nr);
fclose(f);
fclose(g);
return 0;
}