In general, to build a binary tree you are going to need two traversals, in order and pre-order for example.

Which traversal used to construct a binary tree?

If one of the traversal methods is Inorder then the tree can be constructed, otherwise not. Therefore, following combination can uniquely identify a tree. Inorder and Preorder. Inorder and Postorder.

How binary tree is constructed from its traversals?

1) Find index of the maximum element in array. The maximum element must be root of Binary Tree. 2) Create a new tree node 'root' with the data as the maximum value found in step 1. 3) Call buildTree for elements before the maximum element and make the built tree as left subtree of 'root'.