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# Learn how to Discover the Divisors in C

## The problem#

Create a operate named `divisors`/`Divisors` that takes an integer `n > 1` and returns an array with all the integer’s divisors(apart from 1 and the quantity itself), from smallest to largest. If the quantity is prime return the string ‘(integer) is prime’ (`null` in C#) (use `Both String a` in Haskell and `Outcome<Vec<u32>, String>` in Rust).

#### Instance:#

``````divisors(12); // leads to {2, 3, 4, 6}
``````

Possibility 1:

``````#embrace <stddef.h>

void divisors(unsigned n, size_t *z, unsigned *array) {
*z = 0;

for (int i = 2; i <= (n / 2); i++) {
if (n % i == 0)
array[(*z)++] = i;
}
}
``````

Possibility 2:

``````#embrace <stddef.h>

void divisors(unsigned n, size_t *size, unsigned array[]) {
int i;
int j = 0;
for (i = 2; i < (int) n; i++) {
if (n % i == 0) {
array[j] = i;
j++;
}
}
*size = (size_t) j;
}
``````

Possibility 3:

``````#embrace <stddef.h>

void divisors(unsigned n, size_t *z, unsigned *array) {
int len = 0;
for (unsigned i = 2; i < n; i++) {
if (n % i == 0) array[len++] = i;
}
*z = len;
}
``````

## Check circumstances to validate our resolution#

``````#embrace <criterion/criterion.h>
#embrace <stddef.h>

extern void tester(unsigned n, size_t size, const unsigned anticipated[length]);

Check(Sample_Tests, should_pass_all_tests)
{
{ unsigned n =  15; const unsigned anticipated[2] = {3, 5};              tester(n, 2, anticipated); }
{ unsigned n = 253; const unsigned anticipated[2] = {11, 23};            tester(n, 2, anticipated); }
{ unsigned n =  24; const unsigned anticipated[6] = {2, 3, 4, 6, 8, 12}; tester(n, 6, anticipated); }
{ unsigned n =  25; const unsigned anticipated[1] = {5};                 tester(n, 1, anticipated); }
{ unsigned n =  13; const unsigned *anticipated = NULL;                  tester(n, 0, anticipated); }
{ unsigned n =   3; const unsigned *anticipated = NULL;                  tester(n, 0, anticipated); }
{ unsigned n =  29; const unsigned *anticipated = NULL;                  tester(n, 0, anticipated); }
}
``````

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