struct TreeNode{    struct TreeNode *left;    struct TreeNode *right;    int key;};//这里先判断是否为二叉搜索树，其次判断是否为平衡的bool IsAVL(TreeNode *root,int depth){    if (isBST(root)&&isBalance(root,&depth))    return true;    return false;}//判断是否为二叉搜索树bool isBST(TreeNode *root){    if(root == NULL)return true;    if (!isBST(root->left))return false;    if (!isBST(root->right))return false;    TreeNode *cur = root->left;    if (cur != NULL)    {        while(cur->right!=NULL)cur = cur->right;        if(root->key < cur->key)return false;    }    TreeNode *cur = root->right;    if (cur != NULL)    {        while(cur->left!=NULL)cur = cur->left;        if(root->key > cur->key)return false;    }    return true;}//判断是否平衡bool isBalance(TreeNode *root,int *depth){    if (root == NULL)    {        *depth = 0;        return true;    }    int depthl,depthr;    if(!isBalance(root->left,&depthl))return false;    if(!isBalance(root->right,&depthr))return false;    int diff = depthl - depthr;    if(diff > 1 || diff < -1)return false;    *depth = 1+(depthl>depthr?depthl:depthr);    return true;}