/Determinarea nr prime dintr-un sir
#include <stdio.h>
#include <math.h>
int prim(int numar)
{//verifica daca un nr dat este prim sau nu
int i=2,vb=0;
while((i<=(int)sqrt(numar))&&(!vb))
if(!(numar%i++)) vb=1;
if(vb) return 1;
else return -1;
}
int oglindire(int nr)
{//returneaza oglindirea unui nr nat
int i=nr,r=0;
while(i)
{
r=r*10+(i%10);
i=(int)i/10;
}
return r;
}
int interval2prime(int prim1,int prim2)
{
int i;
for(i=prim1+1;i<prim2;i++)
if(prim(i)==-1) return 1;//exista nr prime intre nr date
return -1;//nu exista nr prime intre nr date
}
void main()
{
/*int numar,k;
printf("Introduce numarul:");
scanf("%d",&numar);
printf("Afisarea nr prime pana la numarul introdus!\n");
for(k=2;k<=numar;k++)
if(prim(k)==-1) printf("Numarul %d este prim!\n",k);
else printf("Numarul %d nu este prim!\n",k);*/
/********************************/
int vector[]={1,2,3,4,7,11};
int i,dim;
dim=(int)sizeof(vector)/sizeof(int);
printf("Elem prime ale caror oglindiri sunt tot nr prime:\n");
int prime[10],dimp=0;
for(i=0;i<dim;i++)
{
if((prim(vector[i])==-1) &&(prim(oglindire(vector[i]))==-1))
{
prime[dimp++]=vector[i];
printf("a(%d)=%d\n",i+1,vector[i]);
}
}
/**********************/
printf("Elem prime ale caror oglindiri sunt tot nr prime, si sunt consecutive:\n");
int vb=0;
for(i=0;i<dimp-1;i++)
{
if(prime[i]<prime[i+1])
if(interval2prime(prime[i],prime[i+1])==-1)
printf("a(%d)=%d\n",i+1,prime[i]);
}
if(prime[i-1]<prime[i])
if(interval2prime(prime[i-1],prime[i])==-1)
printf("a(%d)=%d\n",i+1,prime[i]);
/**/
}