get_divisors.c

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

int get_divisors(int, int **);

int main(void) {
	int *divisors;
	int num_divisors = get_divisors(100, &divisors);
	int i;
	
	for (i = 0; i < num_divisors; i++) {
		printf("%d ", divisors[i]);
	}
	printf("\n");
	
	free(divisors);
	return 0;
}

/* get_divisors: Need to pass in a pointer to an array of integers */
int get_divisors(int n, int **result_ptr) {

	int num_divisors = 0;
	int *result = malloc(sizeof(int) * 100);
	
	// 1 is always in the result
	result[num_divisors++] = 1;
	if (n != 1) {
	    result[num_divisors++] = n;
	}
	
	int max = ceil(sqrt(n));
	int divisor = 2;
	while (divisor <= max) {
		if (n % divisor == 0) {
			result[num_divisors++] = divisor;
			
			int other_divisor = n / divisor;
			if (other_divisor > divisor)
				result[num_divisors++] = other_divisor;
		}
		
		divisor++;
	}
	
	*result_ptr = result;

	// Return number of divisors
	return num_divisors;
}