C program to check prime numbers in an array

C program to check prime numbers in an array

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Full Code:


Code Explanation :


In this example, we are going to learn to prime number in array. We have declared an array with certain prime and non-prime numbers, then print the elements with the message 'prime' and 'Not prime'.

We have to check whether number is prime or not from given single dimension array.

Example:

    Input:
    Array elements are: 
    120, 200, 35, 13, 7, 10, 3, 90

    Output:
    120 - Not Prime
    200 - Not Prime
     35 - Not Prime
     13 - Prime
     7 - Prime
     10 - Not Prime
     3 - Prime
     90 - Not Prime

Logic:

  • We have declared an array (arr) with the elements: 120, 200, 35, 13, 7, 10, 3, 90
  • To test the prime numbers, we declare an isPrime() function returning 1, if number is prime and returning 0 if number is not prime.
  • Then we have used a loop with 0 to len-1 (total number of array elements) and call isPrime() by moving array elements one by one (arr[loop]) in main() function.
  • Then we check a print statement condition: (isPrime(arr[loop])?"Prime":"Not Prime")). This return "Prime", if isPrime(arr[loop]) returns 1 and return "Not Prime", if isPrime(arr[loop]) returns 0.

This is the main concept of this program.

If you want to do smae problem without using function then it is very easy.

#include <stdio.h>
int isPrime(int);

int main()
{
	int loop, i, flag; //loop counter
	//declaring array with prime and not prime numbers
	int arr[]={100, 200, 31, 13, 97, 10, 20, 11};
	//calculate length of the array
	int len = sizeof(arr)/sizeof(arr[0]);
	
	//print array elements with message 
	//"prime" or "Not prime"
	for(loop=0; loop < len; loop++)
	{
		flag = 0;
		for(i=2; i < arr[loop] / 2; i++)
		{
			if(arr[loop] % i ==0)
			{
				flag = 1;
				break;
			}
		}
		//flag is 1, if number is not prime
		if(flag == 1){
			printf("%3d - Not Primen",arr[loop]);
		}
		else
		{
			printf("%3d - Primen",arr[loop]);
		}	
	}
	
	printf("n");
	
	return 0;	
}

The algorithm and flowchart of this progrem is:

Algorithm

STEP 1 : Start;

STEP 2 : Declare variable arr[], loop, i and flag;

STEP 3 : Initialize arr[] = {100, 200, 31, 13, 97, 10, 20, 11};

STEP 4 : Get the length of array;

STEP 4 : Repeat this process until loop < len
        STEP 4.1 : flag = 0
        STEP 4.2 : Repeat this process until i < arr[loop]
                STEP 4.2.1 : flag = 1
                STEP 4.2.2 : break
        STEP 4.3 : IF flag == 1 THEN
                    Print prime
                ELSE
                    Print not prime
        STEP 4.4 : loop++

STEP 5 : End

Flowchart

C program to check prime numbers in an array

If you got any problem on understanding this example then please comment below.



Our example mainly covers following topics in any programing

  • Basic Programs
  • Number Programs
  • Array Programs
  • Matrix Programs
  • Pattern Programs
  • String Programs
  • Tree Programs
  • Singly Linked List Programs
  • Circular Linked List Programs
  • Doubly Linked List Programs

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