Question

Сформировать массив простых чисел, не больших заданного. язык Си.

Answer 1

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

bool simpl(int n) {
   int k=1,m;
   m=sqrt(n)+1;
   for (int i=2; i<=m; i++)
   if ((n % i)==0)   {  k=0;  break; }
   return k;
 }

int main() {
    int n,k=0; 
    printf("N = ");  scanf("%i",&n); 
    int a[n];
    for (int i=1; i<=n; i++)
      if (simpl(i)) { a[k]=i;  k++; };
    for (int i=0; i<k; i++)
    printf("%i  ",a[i]);    
    getch();
    return(0);
}

Answer 2

Generating an Array of Prime Numbers in C

To generate an array of prime numbers not greater than a given number in C, you can use the Sieve of Eratosthenes algorithm. This algorithm efficiently finds all primes smaller than a given number. Here's how you can implement it in C:

#include 
#include

void sieveOfEratosthenes(int n) {
    bool prime[n+1];
    memset(prime, true, sizeof(prime));

for (int p = 2; p * p <= n; p++) {
        if (prime[p] == true) {
            for (int i = p * p; i <= n; i += p)
                prime[i] = false;
        }
    }

printf("Prime numbers less than or equal to %d are: ", n);
    for (int p = 2; p <= n; p++) {
        if (prime[p])
            printf("%d ", p);
    }
}

int main() {
    int limit;
    printf("Enter the limit: ");
    scanf("%d", &limit);
    sieveOfEratosthenes(limit);
    return 0;
}

In this code: 1. We declare an array `prime` of boolean values to mark numbers as prime or not. 2. We iterate through the numbers and mark the multiples of each number as not prime. 3. Finally, we print the prime numbers less than or equal to the given limit.

Note: This code uses the Sieve of Eratosthenes algorithm to efficiently find prime numbers.