A sympotic performance will be linear in O(n). That is the tree created will be skew symmetric. Identical keys should be attached either as left or right child of the parent, wherever positions are available. For eg. 18,3,5,2,4,7,2,9,2,16,2,11,2,10,2
The creation of the tree should be as follows:
i.e. similar keys should not skew to the BST. Then performance will become inferior.