/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class BSTIterator {
public:
   stack<TreeNode*> stk;
    BSTIterator(TreeNode* root) {
        if(root){
stk.push(root);
        if(root->left){
            TreeNode*left=root->left;
            while(left){
                stk.push(left);
                left=left->left;
            }
        }
        }

    }

    /** @return the next smallest number */
    int next() {

            TreeNode*top=stk.top();
            stk.pop();
            if(top->right){
                TreeNode*right=top->right;
                stk.push(right);
                if(right->left){
                    TreeNode*left=right->left;
            while(left){
                stk.push(left);
                left=left->left;
            }
                }
            }
         return top->val;
    }

    /** @return whether we have a next smallest number */
    bool hasNext() {
        return !stk.empty();
    }
};

/**
 * 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();
 */