/**

 * Definition for binary tree

 * struct TreeNode {

 *     int val;

 *     TreeNode *left;

 *     TreeNode *right;

 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

 * };

 */

class BSTIterator {

public: queue<int> Q;

public:

    BSTIterator(TreeNode *root) {

        inOrder(root, Q);

    }

    void inOrder(TreeNode* root, queue<int>& Q) {

        if(root != NULL) {

            inOrder(root->left, Q);

            Q.push(root->val);

            inOrder(root->right, Q);

        }

    }

    /** @return whether we have a next smallest number */

    bool hasNext() {

        return !Q.empty();

    }

    /** @return the next smallest number */

    int next() {

        int next_min = Q.front();

        Q.pop();

        return next_min;

    }

};

/**

 * Your BSTIterator will be called like this:

 * BSTIterator i = BSTIterator(root);

 * while (i.hasNext()) cout << i.next();

 */