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Code: Select all

#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
bool prime(long long int j)
{    bool fl=true;
     if(j==0 && j==1)
     return true;
     else
     {
     for (long long int t=2;t<=sqrt(j);t++)
     {
     if(j%t==0)
     {        
        fl=false;
              }
              }
     if(fl==false)
     return false;
     if(fl==true)
     return true;
     }
     }
int main()
{
    int a,b,k=2;
    int v[10001];
    v[0]=0;v[1]=1;
    for (int h=3;h<=10001;h=h+2)
    {
        if(prime(h)==true)
        {
         v[k]=h;
         k++;
         }
         }
    while (cin>>a>>b)
    {
           bool flag1=false,flag2;
           int c2=0;        
           
              for (int i=a;i<=b;i++){flag2=true;   
               long long int m=i*i+i+41;
               
               for(int q=2;q<k && v[q]<sqrt(m);q++)
               {if(m%v[q]==0)
                flag2=false;
               }
               if (flag2==true && i!=40)
               c2+=1;
               
               }
               double pr;
               pr=(double(c2)/double(b-a+1))*100.0;
               cout<<setiosflags(ios::fixed)<<setprecision(2)<<pr<<endl;
               }
               return 0;
               }

Code: Select all

#include<stdio.h>
#include<math.h>

int count[10005];

int main(){
	int flag,total,temp,a,b;
	long prime,z;
	double ans;
	count[0]=1;
	for (int i=1;i<10005;i++){
		prime=i*i+i+41;
		flag=1;
		if (prime%2==0) flag=0;
		else {
			z=ceil(sqrt(prime));
			for(int c=3;c<=z;c+=2){
				if (prime%c==0){
					flag=0;
					break;
				}
			if (flag==0) break;
			}
		}
		count[i]=count[i-1]+flag;
	}
	while(scanf("%d %d",&a,&b)==2){
		if ((count[b]==count[a]) && (count[a]==count[a-1])) temp=0;
		else{
			total=b-a+1;
			temp=count[b]-count[a]+1;
		}		
		ans=(temp*100.)/total;
		printf("%.3lf\n",ans);
	}
	return 0;
}

Code: Select all

# include <stdio.h>

int prime[10010];

void genprime()
{
    int i,j;
    
    for(i=0;i<=10010;i++)   prime[i]=i;
    
    prime[0]=prime[1]=0;
     
    for(j=4;j<=10010;j+=2)  prime[j]=0;
    
    for(i=3;i*i<=10010;i+=2)
        if(prime[i])
            for(j=i*i;j<=10010;j+=i)
                prime[j]=0;
}

int isprime(int n)
{
   int i,j;
   
   
   if(n<2 || n%2 == 0 || n%5 == 0)  return 0;
   
   for(i=0;prime[i]*prime[i]<=n;i++)
    if(prime[i])
    if(n%prime[i] == 0)
        return 0;
        
    return 1;
}
        
int main()
{
    int  i,j,m,n;
    double count;
    int flag[10005]={0};
    
    genprime();
    
       for(i=0;i<=10000;i++){
            if(isprime(i*i+i+41))
                flag[i]=1; 
            }
    while(scanf("%d %d",&m,&n) == 2)
    {
        count = 0.0;
     
        
        for(i=m;i<=n;i++){
            if(flag[i])
                count++;
                                          
        }
                
        printf("%.2lf\n",(count/(n-m+1))*100);
    }
return 0;
}