Block trees

Let string S[1..n] be parsed into z phrases by the Lempel-Ziv algorithm. The corresponding compression algorithm encodes S in O(z) space, but it does not support random access to S. We introduce a data structure, block tree, that represents O(zlog⁡(n/z)) space and extracts any symbol of time O(log⁡(n/z)), among other space-time tradeoffs. structure also supports queries are useful for building compressed structures on top Further, trees can built linear scalable manner. Our experiments show offer relevant tradeoffs compared representations highly repetitive strings.