堆排序

void AdjustDown(int a[], int root, int size)  //調整堆
{
	int left = root * 2 + 1;
	int right = left + 1;
	int key = left;
	while (left < size)
	{
		if (right<size&&a[left]>a[right])
		{
			key = right;
		}
		if (a[key] < a[root])
		{
			swap(a[root], a[key]);
			root = key;
			left = root * 2 + 1;
			right = left + 1;
			key = left;
		}
		else
		{
			break;
		}
	}
}
void HeapSort(int a[], int size)
{
	int begin = size / 2 - 1;
	for (; begin >= 0; begin--)
	{
		AdjustDown(a, begin, size);
	}
	int end = size - 1;
	while (end)
	{
		swap(a[0], a[end]);
		AdjustDown(a, 0, end);
		end--;
	}
}