Question

500以内的素数有多少个？分别是多少？

Answer 1

500以内素数有95个具体的自己看下面的图片或者看这个http://wenku.baidu.com/view/a6790775a417866fb84a8e51.html

Answer 2

#include <iostream>
using namespace std;
bool Prime[1000000];

bool* PrimeNum() {
for(int i = 0; i < 1000; i++) {
if(Prime[i] == true)
continue;
for(int j = i*2; j < 1000000; j+=i)
Prime[j] = true;
}
return Prime;
}

int main() {
int n;
memset(Prime,false,sizeof(Prime));
Prime[0] = Prime[1] = 1;
while(cin >> n) {
PrimeNum();
if(Prime[n] == false)
cout << n << " is prime!" << endl;
else cout << n << " is not prime!" << endl;
}
return 0;
}

1000000以内的素数……