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Regular Expression Search with Suffix Arrays
- pronoiac 11y agoOh, cool! I've looked into suffix trees and suffix arrays, by way of investigating how diff works. While I found suffix trees hard to understand, this is a great explanation of suffix arrays. Suffix arrays can take much less space - I've heard 1/4 as much space? - than suffix trees.
- TheLoneWolfling 11y agoI wonder how efficient this is in the worst case. In particular, something like [02468]+ (or something similar. A discontinuous range repeated a bunch of times.) I wonder how this would compete with a full suffix tree or trie - or better yet, suffix DAG, which will generally take a whole lot more time to construct but may be (much) smaller.
- adamtj 11y ago> but may be (much) smaller. The suffix array is already very small. It doesn't store the full suffixes, just the numbers. It's basically a list of pointers with one pointer for each character in the input data. The characters aren't duplicated, unlike a suffix tree. In fact, the suffix array is just the leaf nodes of a suffix tree in depth-first order. The internal nodes are omitted. Further, you can store it as an array instead of a linked list, meaning you halve the number of pointers to store.
- TheLoneWolfling 11y agoI mean that a suffix DAG would be smaller than a full suffix tree, sorry that that was confusing. I am aware that a suffix array is smaller than a suffix DAG.