【数据结构】二叉树的节点数，叶子数，第K层节点数，高度，查找x节点，判断是否为完全二叉树等方法【上】

typedef char BTDataType;
typedef struct BinaryTreeNode
{
  BTDataType _data;
  struct BinaryTreeNode* _left;
  struct BinaryTreeNode* _right;
}BTNode;

// 二叉树销毁
void BinaryTreeDestory(BTNode* root)
{
  if (root == NULL)
  {
    return;
  }
  BinaryTreeDestory(root->_left);
  BinaryTreeDestory(root->_right);
  free(root);
}

//构建节点
BTNode* BuyNode(int x)
{
  BTNode* node = (BTNode*)malloc(sizeof(BTNode));
  if (node == NULL)
  {
    perror("malloc fail");
    exit(-1);
  }
  node->_data = x;
  node->_left = NULL;
  node->_right = NULL;
  return node;
}

//树的高度
int TreeHeight(BTNode* root)
{
  if (root == NULL)
    return 0;
  return fmax(TreeHeight(root->_left), TreeHeight(root->_right)) + 1;
}

// 二叉树节点个数
int BinaryTreeSize(BTNode* root)
{
  return root == NULL ? 0 : BinaryTreeSize(root->_left) 
  + BinaryTreeSize(root->_right) + 1;
}