Twin primes are pairs of primes that are separated by 2 exam

Twin primes are pairs of primes that are separated by 2, example:

     3/5 are twin primes, 5/7 are twin, and 11/13 are also twin primes.

Write a c program that can identify twin primes and ignoring the first 99,999 pairs, what is the 100,000 twin prime? (hint: you should get the values: 18409199, 18409201)

In addition, you need to have the program determine how long it takes to calculate this pair. A reasonable target is approx. 8 seconds or less. Display the time in milli-seconds.

     Example:

            Starting….

18409199, 18409201

Completed in: 7.438 seconds

I suggest using the ‘C’ library function: clock()   which returns a time count in milliseconds. If you perform the following sequence, you will be able to determine how long the program takes to complete:

int time_beg, time_end, time_elapsed;

time_beg = clock();

Do_Prime_Number_Calc();

time_end = clock();

time_elapsed = time_end – time_beg;

Solution

PROGRAM CODE:

/*
* TwinPrime.c
*
* Created on: 22-Jan-2017
* Author: kasturi
*/

#include <stdio.h>
#include <time.h>

int checkPrime(long n)
{
   for(long i=2; i<=n/2; ++i)
   {
// condition for nonprime number
if(n%i==0)
{
return 0;
}
}
return 1;
}

void Do_Prime_Number_Calc()
{
   long counter = 0;
   long number = 3;
   int prime1 = checkPrime(number);
   while(counter!=100001)
   {
       number = number+2;
       int prime2 = checkPrime(number);
       if(prime1==1 && prime2==1)
       {
           counter++;
           prime1 = 1;
       }else if(prime1 == 1 && prime2 == 0)
       {
           prime1 = 0;
           prime2 = 0;
           number = number+2;
           prime1 = checkPrime(number);
       }

   }
   printf(\"Pair: %ld & %ld\", number-4, number-2);
}

int main(void) {
clock_t start_t, end_t, total_t;
start_t = clock();
Do_Prime_Number_Calc();
end_t = clock();
total_t = end_t - start_t;
printf(\"Time elapsed: %ld\", total_t/CLOCKS_PER_SEC);
   return 0;
}

The above program will have to run for a considerable time to give the output. My machine has less configuration and hence will take a lot of time. This will give result sooner in a high configuration machine.