How to destory a binary tree?

I created the following binary tree, but I don't know why the code that destorys the binary tree doesn't work.

typedef char BTDataType;

typedef struct BinaryTreeNode
{
	BTDataType data;
	struct BinaryTreeNode* left;
	struct BinaryTreeNode* right;
}BTNode;

BTNode* BinaryTreeCreate(BTDataType* a, int* pi)
{
	BTDataType data = a[(*pi)++];
	if (data == '#')
		return NULL;
	BTNode* Node = (BTNode*)malloc(sizeof(BTNode));
	if (Node == NULL)
	{
		perror("malloc fail");
		return NULL;
	}
	Node->data = data;
	Node->left = BinaryTreeCreate(a, pi);
	Node->right = BinaryTreeCreate(a, pi);
	return Node;
}

void BinaryTreeDestory(BTNode** root) {
	if (root == NULL || *root == NULL) {
		return;
	}
	BinaryTreeDestory(&(*root)->left);
	BinaryTreeDestory(&(*root)->right);
	free(*root);
	*root = NULL;
        return;
}

int main()
{
    BTDataType a[] = "ABD##E#H##CF##G##";
    int i = 0;

    BTNode* root = BinaryTreeCreate(a, &i);
    BinaryTreeDestory(&*root);
}

I want to know where the code for destroying the binary tree is wrong and how to correct it

There should be a compiler warning for this line

BinaryTreeDestory(&*root);

because the argument is the wrong type, and &*root is just root. The line should be

BinaryTreeDestory(&root);

Note that BinaryTreeCreate() doesn't order the data, which can be seen from a simple BinaryTreeShow() function I added.

void BinaryTreeShow(BTNode* root) {
    if (root == NULL) {
        return;
    }
    BinaryTreeShow(root->left);
    printf("%c", root->data);
    BinaryTreeShow(root->right);
}

I think the code is otherwise OK, but BinaryTreeDestory() is needlessly clumsy passing the address of the parent. It can be done by returning when the node pointer is NULL and then the caller can free() the node.

Weather Vane provided the correct answer. Some of the confusion could be from passing pointers to pointers. A simplification of your code could be simply be this and rely on the caller to explicitly deal with setting the free'd pointer to NULL. Then you can just pass the root pointer without taking the address of it.

void BinaryTreeDestory(BTNode* root) {
    if (root == NULL) {
        return;
    }

    BinaryTreeDestory(root->left);
    BinaryTreeDestory(root->right);
    free(root);
    return;
}

int main()
{
    BTDataType a[] = "ABD##E#H##CF##G##";
    int i = 0;

    BTNode* root = BinaryTreeCreate(a, &i);
    BinaryTreeDestory(root);
    root = NULL; // not needed, but it is good form
}