FGL Homework: Sort Int Array

/*
    Alaestor, discord: http://public.FutureGadgetLab.net

    Your task is to create an array sorting function.

    Given the following source, you must write the "sort" function.
    It should be simplistic and be your own function. Don't call an existing
    sorting function, and don't just copy+paste one from the web.
*/
#include <iostream>
#include <cstdio>
#include <ctime>

void sort(int* arr, const std::size_t size);
void debugPrint(int* arr, const std::size_t size);
bool isSorted(int* arr, const std::size_t size);

int main()
{
    srand(time(nullptr));

    constexpr const std::size_t max_index = 30;
    int array[max_index];
    for (std::size_t i = 0; i < max_index; ++i) array[i] = rand() - RAND_MAX/2;

    sort(array, max_index); // the function I want you to make
    //debugPrint(array, max_index);

    std::cout
        << "The array sort you made was a "
        << (isSorted(array, max_index) ? "Success." : "Failure!")
        << std::endl;
}

void sort(int* arr, const std::size_t size)
{ // you are only allowed to write code in this

//////////////////////////////////////////////////////////////////////
    // bubblesort example
    // the following is a test and should be removed before giving to student
    int temp;
    std::size_t n = size;
    std::size_t newn;
    do
    {
        newn = 0;
        for (std::size_t i = 1; i < size; ++i)
        {
            if (arr[i-1] > arr[i])
            {
                temp = arr[i-1];
                arr[i-1] = arr[i];
                arr[i] = temp;
                newn = i;
            }
        }
        n = newn;
    }
    while (n != 0);
//////////////////////////////////////////////////////////////////////
}

void debugPrint(int* arr, const std::size_t size)
{ // for debugging purposes
    for (std::size_t i = 0; i < size; ++i)
        std::cout << arr[i] << (i+1 != size ? ", " : "\n");

    std::cout << std::endl;
}

bool isSorted(int* arr, const std::size_t size)
{ // this is the code that tests if you've succeeded or failed
    for (std::size_t i = 0; i < size - 1; ++i)
        if (!(arr[i] <= arr[i+1])) return false;

    return true;
}