#include<stdio.h>
int a (int n)
{
int i;
for(i=2;i<=(n-1)/2;i++)
{
if(n%i==0)
{
return (0);
}
}
return (1);
}
int main()
{
int i,j,k,s,t;
printf("following are palindrome primes not greater than 1000:\n");
for(i=0;i<=9;i++)
{
for(j=0;j<=9;j++)
{
for(k=0;k<=9;k++)
{
s=i*100+j*10+k;
t=k*100+j*10+i;
if(i==0&&j==0)
{
t/=100;
}
else if(i==0)
{
t/=10;
}
if(s>10 && s==t && a(s))
{
printf("%d\t",s) ;
}
}
}
}
}
要发就发
#include<stdio.h>
#include <math.h>
#define NUM 320
int number [NUM];
int fflag(int i)
{
int j;
if(i<=1)
{
return (0);
}
if(i==2)
{
return (1);
}
if(!(i%2))
{
return (0);
}
for(j=3;j<=(int)(sqrt((double)i)+1);j+=2)
{
if(!(i%j))
{
return (0);
}
}
return (1);
}
int main()
{
int i,j,count=0;
printf("there are following primes sequences in first row:\n");
for(j=0,i=3;i<=1993;i+=2)
{
if(fflag(i))
{
number[j++]=i;
}
}
for(j--;number[j]>1898;j--)
{
for(i=0;number[j]-number[i]>1898;i++)
{
;
}
if(number[j]-number[i]==1898)
{
printf("(%d).%3d,.......,%d\n",++count,number[i],number[j]);
}
}
}