Simple and efficient fully-functional succinct trees

The fully-functional succinct tree representation of Navarro and Sadakane (ACM Transactions on Algorithms, 2014) supports a large number of operations in constant time using 2n + o(n) bits. However, the full idea is hard to implement. Only a simplified version with O(lg n) operation time has been implemented and shown to be practical and competitive. We describe a new variant of the original idea that is much simpler to implement and has worst-case time O(lg lg n) for the operations. An implementation based on this version is experimentally shown to be superior to existing implementations.