Prime prime screening of screening

This is a prime number screening most simplest way

The core idea is to use factor, a 0-1 mark

#define maxn 1000000

int prime[maxn + 5] = {1, 1, 0};

void init（）{
	for(int i = 1; i <= maxn ; i++){
		if(prime[i]) continue;
	for(int j = 2 * i; j <= maxn; j += i){
		prime[j] = 1;
	}
}