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APC-PRAC-022.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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  • Recursion
  • Pointers
  • Iteration

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Source Code

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

bool checkPrime(int num)
{
    if (num < 2)
        return false;
    if (num == 2)
        return true;
    if (num % 2 == 0)
        return false;
    int limit = (int)sqrt(num);
    for (int i = 3; i <= limit; i += 2)
        if (num % i == 0)
            return false;
    return true;
}

int reverseNumber(int num)
{
    int reverse = 0;
    while (num > 0)
    {
        reverse = (reverse * 10) + (num % 10);
        num /= 10;
    }
    return reverse;
}

int main()
{
    int num;
    printf("Enter the number : ");
    scanf("%d", &num);
    if (!checkPrime(num))
    {
        printf("\nInput %d is not a prime number.", num);
        return 0;
    }
    if (checkPrime(reverseNumber(num)))
        printf("\nInput %d is a twisted prime number.", num);
    else
        printf("\nInput %d is not a twisted prime number.", num);
    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 (APC-PRAC-022.c):

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

    bool checkPrime(int num)
    {
        if (num < 2)
            return false;
        if (num == 2)
            return true;
        if (num % 2 == 0)
            return false;
        int limit = (int)sqrt(num);
        for (int i = 3; i <= limit; i += 2)
            if (num % i == 0)
                return false;
        return true;
    }

    int reverseNumber(int num)
    {
        int reverse = 0;
        while (num > 0)
        {
            reverse = (reverse * 10) + (num % 10);
            num /= 10;
        }
        return reverse;
    }

    int main()
    {
        int num;
        printf("Enter the number : ");
        scanf("%d", &num);
        if (!checkPrime(num))
        {
            printf("\nInput %d is not a prime number.", num);
            return 0;
        }
        if (checkPrime(reverseNumber(num)))
            printf("\nInput %d is a twisted prime number.", num);
        else
            printf("\nInput %d is not a twisted prime number.", num);
        return 0;
    }