[转]筛选法求素数

#include <iostream> #include <fstream>
using namespace std;
const int LENGTH=500;
bool Array[LENGTH]={false};
int main()
{
    ofstream FILE("Result.txt",ios::app);
    for (int i=2;i<=LENGTH;++i)
    {
        if (Array[i]==false)
        {
            cout<<i<<" ";
            FILE<<i<<" ";
            for (int j=i+i;j<=LENGTH;j+=i)//HERE!筛选法求素数!
            {
                Array[j]=true;
            }
        }
    }
    cout<<endl;
    FILE<<endl;
    FILE.close();
}