primes.c

#include <stdio.h>
#include <stdlib.h> // Include stdlib for malloc and free
#include <limits.h>
#include <stdbool.h>
#include <string.h>

void sieve_of_eratosthenes(unsigned long n) {
    // Dynamically allocate memory for the prime array on the heap
    bool *prime = (bool *)malloc((n + 1) * sizeof(bool));
    if (!prime) {
        fprintf(stderr, "Memory allocation failed\n");
        exit(1); // Exit the program if memory allocation fails
    }

    // Initialize all entries as true
    memset(prime, true, (n + 1) * sizeof(bool));

    // 0 and 1 are not prime numbers
    prime[0] = prime[1] = false;

    // Start from the first prime number, which is 2
    for (unsigned long p = 2; p * p <= n; p++) {
        // If prime[p] is not changed, then it is a prime
        if (prime[p]) {
            // Update all multiples of p
            for (unsigned long i = p * p; i <= n; i += p)
                prime[i] = false;
        }
    }

    // Print all prime numbers
    uint min, max, count;
    min = max = count = 0;
    
    for (unsigned long p = 2; p <= n; p++)
        if (prime[p]) {
            min = p;
            break;
        }
        
    for (unsigned long p = 2; p <= n; p++)
        if (prime[p]) {
            max = p;
            count++;
        }
        
        
    printf("min: %u max: %u count: %u\n", min, max, count);

    // Free the allocated memory
    free(prime);
}

int main() {
    unsigned long max_value = UINT_MAX; // Maximum value of unsigned 32-bit int
    printf("Prime numbers up to %u are: ", max_value);
    sieve_of_eratosthenes(max_value);
    return 0;
}