C++ 堆排序

// 堆排序-小堆排序
void SmallHeap(int arr[], int parent, int length)
{
	int temp = arr[parent];
	int child = parent * 2 + 1; 

	while (child < length)
	{
		if (child + 1 < length && arr[child] > arr[child + 1])
		{
			child++;		// 如果左子节点大于右子节点，则当前节点置成右节点
		}

		if (temp <= arr[child])  // 判断父节点比子节点小，则建堆完成
		{
			break;
		}
		else
		{
			arr[parent] = arr[child]; // 交换父节点与子节点
			parent = child;		// 父节点更新为原子节点
			child = parent * 2 + 1;
		}
		 
	}
	arr[parent] = temp;

}

// 大堆
void BigHeap(int arr[], int parent, int length)
{
	int temp = arr[parent];
	int child = parent * 2 + 1;
	while (child < length)
	{
		if (child + 1 < length && arr[child] < arr[child+1])
		{
			child++;
		}
		if (temp > arr[child])
		{
			break;
		}
		else
		{
			arr[parent] = arr[child];
			parent = child;
			child = parent * 2 + 1;
		}

	}
	arr[parent] = temp;


}


void HeapSort(int arr[], int length)
{
	// 建堆 子节点和父节点关系parent = child*2+1  
	// 注：最后一个元素下标length-1
	for (int i = (length-2)/2; i >= 0; i--)
	{  
		//SmallHeap(arr, i, length);  // 建堆是从下往上依次遍历根节点
		BigHeap(arr, i, length);
	}

	// 交换
	for (int i = length-1; i >= 1; i--)
	{
		int temp = arr[0];
		arr[0] = arr[i];
		arr[i] = temp;
		//SmallHeap(arr, 0, i);     // 调整堆，只需要调整索引号为0的父节点即可
		BigHeap(arr, 0, i);
	}
}

int main()
{
	int array[] = { 5,3,1,6,9,8,4 };
	//int array[] = { 8,2,4,1,5,7 };
	for (int i = 0; i < sizeof(array)/sizeof(int); i++)
	{
		cout << array[i] << (i != sizeof(array) / sizeof(int) ? " ": "\n");
	}
	cout << "\n";

	//BubbleSort(array, sizeof(array) / sizeof(int));
	//QuickSort(array, 0, sizeof(array) / sizeof(int) - 1);
	//SelectSort(array, sizeof(array) / sizeof(int));
	//InsertSort(array, sizeof(array) / sizeof(int));
	//ShellSort(array, sizeof(array)/sizeof(int));
	//MergeSort(array, 0, sizeof(array) / sizeof(int)-1);

	HeapSort(array, sizeof(array) / sizeof(int));


	int i = 0;
	while (i < sizeof(array)/sizeof(int))
	{
		cout << array[i] << (i == (sizeof(array) / sizeof(int)) ? "\n": " ");
		i++;
	}	



	return 0;
}