void inorder (Node * root){ if (root) { inorder(root->left) coutvalue; inorder(root->right) } }

This is a binary tree, not a binary search tree. Thus, in order traversal may not work.

If it isn't a binary search tree, then just traverse the tree in any which way and put the elements into a min heap. Then iteratively pop the min off the top to return smallest to greatest. Traversal would take O(n), building the min heap is also O(n), and popping min off n times is also O(n) so total is O(n).

In order binary tree traversal