c++ 堆排序

只需要heapify

时间复杂度o（nlogn）

void heapify(int index,int heapSize,int *heapArray)
{
	int left = index * 2 + 1;
	while (left < heapSize)
	{
		int largest = left + 1 < heapSize && heapArray[left + 1] > heapArray[left] ? left + 1 : left;
		if (heapArray[index] > heapArray[largest])
			break;

		swap(heapArray[index], heapArray[largest]);
		index = largest;
		left = index * 2 + 1;
	}
}
void heapsort(int *arr,int length)
{
	for (int i = length - 1; i >= 0; i--)
	{
		heapify(i, length, arr);
	}
	swap(arr[0], arr[--length]);
	while (length > 0)
	{
		heapify(0, length, arr);
		swap(arr[0], arr[--length]);
	}
}

int main()
{
	int arr[]={ 5, 3, 2, 8, 9, 6, 7, 1, 4 };
	heapsort(arr, sizeof(arr) / sizeof(arr[0]));
	for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
	{
		cout << arr[i] << ' ';
	}
	return 0;
}

输出：

1 2 3 4 5 6 7 8 9