C++のスタックソート

template
void maxHeapify(T arr[], int index, int heapSize) {
  int maxIndex = index;
  int left = 2 * index + 1;
  int right = left + 1;
  if (left < heapSize && arr[index] < arr[left]) {
    maxIndex = left;
  }
  if (right < heapSize && arr[maxIndex] < arr[right]) {
    maxIndex = right;
  }
  if (maxIndex != index) {
    swap(arr[maxIndex], arr[index]);
    maxHeapify(arr, maxIndex, heapSize);
  }
    return;
}
template
void build(T arr[], int heapSize) {
     for (int i = heapSize / 2 - 1; i >= 0; i--) {
        maxHeapify(arr, i, heapSize);
     }
}
template
void sort(T arr[], int heapSize) {
     build(arr, heapSize);
     for (int i = heapSize - 1; i > 0; i--) {
        swap(arr[0], arr[i]);
        maxHeapify(arr, 0, i);
     }
}
template
void swap(T &a, T &b) {
     T temp = a;
     a = b;
     b = temp;
}