Question

How to check if a number is prime cyclops in C

Answer 1

// A number with odd number of digits and zero in the center is cyclops number

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

bool isCyclopsNumber(int n) {
    if (n == 0) {
        return true;
    }

    int m = n % 10;
    int count = 0;
    while (m != 0) {
        count++;
        n /= 10;
        m = n % 10;
    }

    n /= 10;
    m = n % 10;
    while (m != 0) {
        count--;
        n /= 10;
        m = n % 10;
    }

    return n == 0 && count == 0;
}

bool isPrime(int n) {
    if (n < 2) 
        return false;

    double total = sqrt(n);
    for (int i = 2; i <= total; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}

int main(void) {

    int n = 209;
    puts(isCyclopsNumber(n) && isPrime(n) ? "yes" : "no");

    n = 503;
    puts(isCyclopsNumber(n) && isPrime(n) ? "yes" : "no");

    return 0;
}






/*
run:

no
yes

*/

 

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