#include<iostream>#include<cmath>using namespace std;int prime(int n){ for(int i=2;i<=sqrt(double(n));i++) { if(n%i==0) return 0; } return 1;}int main(){ int N; cout<<"请输入一个数int："; while(1) { cin>>N; if(!cin||N<2) { cin.clear(); cin.ignore();//清除当前行 cout<<"请重新输入！"; continue; } break; } int total=0; for(int i=2;i<=N;i++) { if(prime(i)) { cout<<i<<endl; total++; } } cout<<"一共有"<<total<<"个素数。"; system("pause");}原文：http://1624912549.blog.51cto.com/10534998/1734671