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Write a C Program to count prime numbers and display them using recursion

robaa
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2022-11-25
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Write a C Program to count prime numbers and display them in descending order using recursion. Here’s simple Program to count prime numbers and display them in descending order using recursion in C Programming Language.

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robaa
2022-11-25
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Recursion : :

  • Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
  • The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
  • Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

Below is the source code for C Program to count prime numbers and display them in descending order using recursion which is successfully compiled and run on Windows System to produce desired output as shown below :

 
 

SOURCE CODE : :

/* C Program to count prime numbers and display them in descending order using recursion */


#include<stdio.h>
#include<math.h>

int countPrimes(int a, int b);
int isprime(int n);

int main()
{
        int a,b;
        printf("Enter values of a and b :");
        scanf("%d %d",&a,&b);
        printf("\n\nTotal prime numbers = %d\n",countPrimes(a,b));

        return 0;
}


countPrimes(int a, int b)
{
        if(a>b)
                return 0;
        if(isprime(b))
        {
                printf("%d  ",b);
                return 1 + countPrimes(a,b-1);
        }
        else
                return countPrimes(a,b-1);
}

int isprime( int n)
{
        int i;
        for(i=2; i<=sqrt(n); i++)
                if(n%i == 0)
                    return 0;
        return 1;
}

OUTPUT  : :

***************OUTPUT***************


***************FIRST RUN************

Enter values of a and b :
2
100

97  89  83  79  73  71  67  61  59  53  47  43  41  37  31  29  23  19
17  13  11  7  5  3  2

Total prime numbers = 25



***************SECOND RUN************


Enter values of a and b :
5
50

47  43  41  37  31  29  23  19  17  13  11  7  5

Total prime numbers = 13

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C Recursion Solved Programs – C Programming
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