Substring index

In computer science, a substring index is a data structure which gives substring search in a text or text collection in sublinear time. If you have a document $S$ of length $n$, or a set of documents $D=\{S^1,S^2, \dots, S^d\}$ of total length $n$, you can locate all occurrences of a pattern $P$ in $o(n)$ time. (See Big O notation.)

The phrase full-text index is also often used for an index of all substrings of a text. But is ambiguous, as it is also used for regular word indexes such as inverted files and document retrieval. See full text search.

Substring indexes include:

• Suffix tree
• Suffix array
• N-gram index, an inverted file for all N-grams of the text
• Compressed suffix array^[1]
• FM-index
• LZ-index

References

1. R. Grossi and J. S. Vitter, Compressed Suffix Arrays and Suffix Trees, with Applications to Text Indexing and String Matching, SIAM Journal on Computing, 35(2), 2005, 378-407.