Write a C program to find all emirp numbers between 1 and 1000 1 and 1000 inclusive?

Answer 1

/* emirp_1000.c j. adams

*

* Program to generate prime numbers that are emirps

*

*

* compile with $> gcc -o emirp_1000 emirp_1000.c -lm

*

*

*/

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include <math.h>

#define MAX_RANGE 1000

int main(void)

{

int p = 11;

int p2 = 0;

int itr = 0;

int cnt = 0;

int rev = 0;

int skip_val[]= {2, 4, 2, 2, 2, 4, 2, 2, 2, 4, 2, 2, 2, 4, 2, 2};

while(p < MAX_RANGE)

{

cnt = 16;

itr = 0;

while(cnt--)

{

// check p for primeness.

if(isit_prime(p))

{

p2 = p;

// reverse p

while(p2 > 0)

{

rev = rev * 10 + (p2 % 10);

p2 = p2/10;

}

// If rev != p (palindrome) and rev is prime

if((rev ^ p)&&(isit_prime(rev)))

printf("\n%d", p);

}

rev = 0;

p = p += skip_val[itr++];

}

}

printf("\n");

return 0;

}

int isit_prime(int n)

{

int k = 0;

if (n 0)

return 0;

return 1;

}