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

int _compare_ints(const void* a1, const void* a2) {
    int const* a_n1 = a1;
    int const* a_n2 = a2;
    int n1 = *a_n1;
    int n2 = *a_n2;
    if(n1 < n2) {
        return -1;
    }
    else if(n1 == n2) {
        return 0;
    }
    else {
        assert(n1 > n2);
        return 1;
    }
}

int main(int argc, char* argv[]) {
    int numbers[] = { 4, 1, 3, 2 }; 
    size_t num_numbers = sizeof numbers / sizeof numbers[0];  // Do not use for ▒▒▒* !!!

    // Sort array using qsort(…)
    qsort(numbers, num_numbers, sizeof numbers[0], _compare_ints);

    assert(numbers[0] == 1 && numbers[1] == 2 && numbers[2] == 3 && numbers[3] == 4);
    return EXIT_SUCCESS;
}
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