二叉树的运用（递归)(遍历方式)(简洁.含代码,习题）

//Preorder，Inorder，postorder，代码区别在于打印位置
void Order(BTNode* root) {
	if (root == NULL) {
		printf("NULL ");
		return;
	}
	printf("%d ", root->data);//Preorder前序
	Order(root->left);
    printf("%d ", root->data);//Inorder中序
	Order(root->right);
    printf("%d ", root->data);//postorder后序
}

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

void LevelOrder(BTNode* root)
{
	Queue q;
	QueueInit(&q);
	if (root)
		QueuePush(&q, root);//入队列

	while (!QueueEmpty(&q))
	{
		BTNode* front = QueueFront(&q);//保存队列头指针
		QueuePop(&q);//出队列
		printf("%d ", front->data);

		if(front->left)
			QueuePush(&q, front->left);
		if (front->right)
			QueuePush(&q, front->right);
	}
	QueueDestroy(&q);
}

int TreeSize(BTNode* root)
{
	return root == NULL ? 0 : 
			TreeSize(root->left) 
			+ TreeSize(root->right) 
			+ 1;
}

int TreeHeight(BTNode* root)
{
	if (root == NULL)
		return 0;

	int leftHeight = TreeHeight(root->left);//保存递归的值
	int rightHeight = TreeHeight(root->right);

	return leftHeight > rightHeight ? leftHeight + 1 : rightHeight + 1;
}

int TreeKLevel(BTNode* root, int k)
{
	assert(k > 0);

	if (root == NULL)
		return 0;
	
	if (k == 1)
		return 1;

	return TreeKLevel(root->left, k - 1)
		+ TreeKLevel(root->right, k - 1);
}

void TreeDestory()
{
   if(root==NULL)
     {
      return;
      }
  TreeDestory(root->left);
  TreeDestory(root->right);
  free(root);
}