README.md

Go segtree

A segment tree implementation written in Go.

This library allows storing and retrieving elements indexed by a range. It does this by storing the elements in a segment tree.

Based on:

• go-stree by @toberndo
• Chapter 10.3 of Computational Geometry: Algorithms and Applications rev. 3 by Mark de Berg, Otfried Cheong, Marc van Kreveld and Mark Overmars (ISBN 978-3-540-77973-5)

The elements are sent on a channel as soon as they are found in the tree. This allows efficient querying of e.g multi-dimensional trees (trees containing trees). The elements are not sent in any specific order, however each found element will only be sent once.

Example usages:

tree := new(segtree.Tree)
tree.Push(1, 10, "hello, world")
tree.BuildTree()

results, err := tree.QueryIndex(4)
if err != nil {
	panic(fmt.Sprintf("Failed to query tree: %s", err.Error()))
}

result := <-results
fmt.Println("Found:", result)

An exemplary 2-dimensional segment tree as a tree in a tree:

inner := new(segtree.Tree)
inner.Push(1, 10, "hello, world")
inner.BuildTree()

outer := new(Tree)
outer.Push(0, 99, inner)
outer.BuildTree()

resultsOuter, err := outer.QueryIndex(10)
if err != nil {
	panic(fmt.Sprintf("Failed to query outer tree: %s", err.Error()))
}

result := <-resultsOuter
resultsInner, err := result.(*Tree).QueryIndex(4)
if err != nil {
	panic(fmt.Sprintf("Failed to query inner tree: %s", err.Error()))
}

result = <-resultsInner
fmt.Println("Found:", result.(string))

The library also allows to pretty print the content of the tree for easy debugging.

Example:

tree := new(segtree.Tree)
tree.Push(1, 10, "hello, world")
tree.Push(5, 6, "how are you today?")
tree.Push(9, 45, "test")
tree.BuildTree()

tree.Print()

State of this package

I'm still experimenting with walking the tree concurrently using go routines, but at first sight this does not have any real benefits. I will commit my benchmarks once I have them properly defined so that performance changes can be tracked consistently.

I'm also still experimenting with "real" multi-dimensional segment trees.

However there are no planned changes to the interface of this package, so it should be safe to use it in your project.