Construct a binary tree such that the Post-order traversal should give the sorted result

Since the root is visited last, it must contain the largest item. Since the left subtree is visited before the right subtree, all items in the left subtree must be smaller than any item in the right subtree.

So to construct a tree like this you can proceed as follows: If you insert an item which is greater than the root, that item becomes the new root. If you insert an item which is smaller than the root but greater than the root of the left subtree, insert it into the right subtree. Else insert it into the left subtree.