I tried to optimize heap sort algorithm. Instead of recursion, I used cycle:

void max_heapify (int arr[], int heapsize, int i) {
    int left = 2 * i;
    int right = 2 * i + 1;
    int largest = i;
    do {
        if (i != largest) {
            int tmp = arr[i];
            arr[i] = arr[largest];
            arr[largest] = tmp;
            i = largest;
            left = 2 * i;
            right = 2 * i + 1;
        }
        if (left < heapsize && arr[largest] < arr[left])
            largest = left;
        if (right < heapsize && arr[largest] < arr[right])
            largest = right;
    } while (i != largest);
}

void heap_sort (int arr[], int size) {
    int i;
    for (i = size / 2 - 1; i >= 0; i--)
        max_heapify(arr, size, i);
    for (i = size - 1; i > 0; i--) {
        int tmp = arr[i];
        arr[i] = arr[0];
        arr[0] = tmp;
        max_heapify (arr, i, 0);
    }
}

Seems like it's ok, but is there way to improve it?

I tried to optimize heap sort algorithm. Instead of recursion, I used iteration:

void max_heapify (int arr[], int heapsize, int i) {
    int left = 2 * i;
    int right = 2 * i + 1;
    int largest = i;
    do {
        if (i != largest) {
            int tmp = arr[i];
            arr[i] = arr[largest];
            arr[largest] = tmp;
            i = largest;
            left = 2 * i;
            right = 2 * i + 1;
        }
        if (left < heapsize && arr[largest] < arr[left])
            largest = left;
        if (right < heapsize && arr[largest] < arr[right])
            largest = right;
    } while (i != largest);
}

void heap_sort (int arr[], int size) {
    int i;
    for (i = size / 2 - 1; i >= 0; i--)
        max_heapify(arr, size, i);
    for (i = size - 1; i > 0; i--) {
        int tmp = arr[i];
        arr[i] = arr[0];
        arr[0] = tmp;
        max_heapify (arr, i, 0);
    }
}

Seems like it's ok, but is there way to improve it?