1. If root is null then, return null.
2. If root is not null then find the the size of the right subtree of this node.
3. if this size + 1 is equal to k then return this node.
4. If k is less than right size then recurse with root.right i.e. return findKthLargest(root.right, k)
5. Else, recurse through the left subtree with left node and k-rightSize-1. i.e. return findKthLargest(root.left,
k-rightSize-1);
