UVA-10200

<span style="font-size:18px;">#include<cstdio>#include<cmath>int num[10000+11];int judge(int x){for(int i=2;i<=sqrt(x);++i){if(x%i==0)return 0;//不是素数 }return 1;//是素数 }void count(){int i;for(i=0;i<10000+11;++i)num[i]=judge(i*i+i+41); }int main(){count();int a,b;while(scanf("%d%d",&a,&b)!=EOF){double c=0,d=0;for(;a<=b;++a){if(num[a]==0)//非素数 {c+=1.0;}elsed+=1.0;}printf("%.2lf\n",d/(d+c)*100.0+1e-6);}return 0;}</span>