LCP array construction in external memory

One of the most important data structures for string processing-the suffix array-needs to be augmented with the longest-common-prefix (LCP) array in numerous applications. We describe the first external memory algorithm for constructing the LCP array given the suffix array as input. The only previous way to compute the LCP array for data that is bigger than the RAM is to use an external memory suffix array construction algorithm (SACA) with complex modifications to produce the LCP array as a by-product. Compared to the best prior method, our algorithm needs much less disk space (by more than a factor of three) and is significantly faster. Furthermore, our algorithm can be combined with any SACA, including a better one developed in the future.