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Question

I have an array of strings and I need to create a suffix tree out of it in Golang. SuffixArray in Golang does not suffice my needs, because it only accepts byte array (ie of a single string). Could anybody provide pointers for implementation. Thanks in advance.

Answer 1

Here is an example of how to use suffix array to do auto completion. ( playground ).

Note that I joined all the strings together with a prefix of \\x00 which can't occur in the strings first.

package main

import (
    "fmt"
    "index/suffixarray"
    "regexp"
    "strings"
)

func main() {
    words := []string{
        "aardvark",
        "happy",
        "hello",
        "hero",
        "he",
        "hotel",
    }
    // use \x00 to start each string
    joinedStrings := "\x00" + strings.Join(words, "\x00")
    sa := suffixarray.New([]byte(joinedStrings))

    // User has typed in "he"
    match, err := regexp.Compile("\x00he[^\x00]*")
    if err != nil {
        panic(err)
    }
    ms := sa.FindAllIndex(match, -1)

    for _, m := range ms {
        start, end := m[0], m[1]
        fmt.Printf("match = %q\n", joinedStrings[start+1:end])
    }
}

Prints

match = "hello"
match = "hero"
match = "he"

Answer 2

What you want is called generalized suffix tree. A simple way to build such trees is to append a different end marker(symbols not used in any of the strings) to each strings, concatenate them and build a normal suffix tree for the concatenated string. So you just need to add "hello world" to the string set and use:

match, err := regexp.Compile("[^\x00]*wor[^\x00]*")

to get the strings contain "wor". Note that the correct string is joinedStrings[start:end] .

Answer 3

I created implementation of suffix tree with O(n) complexity, where n is length of string: https://github.com/twelvedata/searchindex

More details in my article on Medium https://medium.com/twelve-data/in-memory-text-search-index-for-quotes-on-go-5243adc62c26