如何创建一个存储素数的数组？

Question

Given an array of 8 integers by the user, the program should print out every prime number entered. The program after entering some number stops, I don't know why. Could you tell what I did wrong please? code:

#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
  
int main()
{
    const int N=8;
    int i, j, count, x;
    int arr[N];
    int prime[N];
    j = 2;
    for(i = 0; i < N; i++)
    {
        printf("Enter a number %d:", i + 1);
        scanf("%d", &arr[i]);
        if (arr[i] == 1)
        {   
            prime[i] = arr[i];
            count++;
        }
        else
        {
            do
            {
                x=arr[i] % j;
                if (x != 0)
                    j++;
                else 
                    break;
            }
            while(true);
            if(arr[i] == j)
            {
                prime[i] = arr[i];
                count++;
            }
        }
    }
            
    for (i = 0; i < count; i++)
        printf("%dth prime number:%d\n", i + 1, prime[i]);  
    
    getch();
    
    return 0;
}

Answer 1

If the user enters an integer which is less than the previous one, your program ends up in an infinite loop. You probably meant to initialize j in the else clause, just before the do-while loop.

Also note that you should check the return value from scanf to make sure that an integer was actually entered.

Answer 2

I use a booleen function to check the element in the array is prime or no,then I fill the array of Prime numbers like this:

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

bool Prime(int);

int main()
{
    int N;
    do
    {
       printf("Give me the number of numbers :");
       scanf("%d",&N);
    }while(N<1);//in your array must be minimum 1 element
    int prime[N];
    int arr[N];
    int j=0;

    for(int i=0;i<N;i++)
    {
       do
       {
           printf("Enter a number %d:",i+1);
           scanf("%d", &arr[i]);
       }while(arr[i]<0); //you can write while(arr[i]>1) and you just write if(Prime(arr[i])==true)

       if(arr[i]!=1&&arr[i]!=0&&Prime(arr[i])==true)
       {
          prime[j]=arr[i];
          j++;
       }
   }
   printf("\n\n");
   for(int p=0;p<j;p++)
   {
       printf("%d th prime number:%d\n",p+1,prime[p]);
   }
  return 0;
}


bool Prime(int n)
{
    for(int i=2;i<=(n/2);i++)
    {
         if(n%i==0)
         {
             return false;
         }
    }
    return true;
}