seive-of-eratosthenes

to calculate primes upto n

void SieveOfEratosthenes(int n) {

memset(prime, true, sizeof(prime)); 

for (int p=2; p*p<=n; p++) 
{ 
   
    if (prime[p] == true) 
    { 
        // Update all multiples of p 
        for (int i=p*2; i<=n; i += p) 
            prime[i] = false; 
    } 
} 

for (int p=2; p<=n; p++) 
   if (prime[p]) 
      cout << p << " "; 

}