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P042.c

Problem Statement

Write a program to accept a number and check whether the number is twisted prime or not.

Metadata

Property Detail
Author Amit Dutta amitdutta4255@gmail.com
Date 12 Dec 2025
License MIT License (See the LICENSE file for details)
Difficulty Beginner (index: 2 / 10)

Concepts

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  • Pointers
  • Recursion
  • Sorting (possible)
  • Iteration

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Source Code

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

int main()
{
    int n, t, i, r, rev, prime = 1;
    printf("Enter the number : ");
    scanf("%d", &n);
    for (i = 2; i <= (int)sqrt(n); i++)
    {
        if (n % i == 0)
        {
            prime = 0;
            break;
        }
    }
    if (prime)
    {
        printf("%d is a prime number.", n);
        t = n;
        rev = 0;
        prime = 1;
        while (t > 0)
        {
            r = t % 10;
            rev = rev * 10 + r;
            t = t / 10;
        }
        for (i = 2; i <= (int)sqrt(rev); i++)
        {
            if (rev % i == 0)
            {
                prime = 0;
                break;
            }
        }
        if (prime)
        {
            printf("\n%d and %d are prime numbers.. TWISTED PRIME", n, rev);
        }
        else
        {
            printf("\n%d is non prime", rev);
        }
    }
    else
    {
        printf("\n%d is non prime.", n);
    }
    return 0;
}

Explanation

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    You are explaining a C programming code to a beginner.

    STRICT RULES:

    - Only use the given code. Do NOT assume anything not present.

    - Do NOT add extra examples.

    - Keep explanation clear and short.

    - If something is unclear, say "Not clear from code".

    - Follow the exact format below. Do NOT change headings.

    FORMAT:

    [START]

    ## What it does

    (Explain the overall purpose in 1-2 sentences)

    ## Step-by-step

    (Explain how the code works in steps, simple language)

    ## Key Concepts

    (List concepts like loop, condition, function, etc.)

    ## Notes

    (Mention any limitations, errors, or assumptions)

    [END]

    CODE (P042.c):

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

    int main()
    {
        int n, t, i, r, rev, prime = 1;
        printf("Enter the number : ");
        scanf("%d", &n);
        for (i = 2; i <= (int)sqrt(n); i++)
        {
            if (n % i == 0)
            {
                prime = 0;
                break;
            }
        }
        if (prime)
        {
            printf("%d is a prime number.", n);
            t = n;
            rev = 0;
            prime = 1;
            while (t > 0)
            {
                r = t % 10;
                rev = rev * 10 + r;
                t = t / 10;
            }
            for (i = 2; i <= (int)sqrt(rev); i++)
            {
                if (rev % i == 0)
                {
                    prime = 0;
                    break;
                }
            }
            if (prime)
            {
                printf("\n%d and %d are prime numbers.. TWISTED PRIME", n, rev);
            }
            else
            {
                printf("\n%d is non prime", rev);
            }
        }
        else
        {
            printf("\n%d is non prime.", n);
        }
        return 0;
    }