/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class BSTIterator {
private:
    //得到中序遍历数组res
    void inorder(TreeNode* root, vector<int>& res){
        if(!root) return;
        inorder(root->left, res);
        res.push_back(root->val);
        inorder(root->right, res);
    }
    vector<int> inorderTraversal(TreeNode* root){
        vector<int>ans;
        inorder(root, ans);
        return ans;
    }
    vector<int>arr;
    int idx;
public:
    //初始化列表
    BSTIterator(TreeNode* root): idx(0), arr(inorderTraversal(root)){}
    int next() {
        return arr[idx++];
    }
    bool hasNext() {
        return (idx < arr.size());
    }
};
/**
 * Your BSTIterator object will be instantiated and called as such:
 * BSTIterator* obj = new BSTIterator(root);
 * int param_1 = obj->next();
 * bool param_2 = obj->hasNext();
 */