Skip List Implementation in Go

What is it ?

Skip list is a probabilistic data structure which keeps its elements in order. It behaves like sorted map. It provides O(log n) insertion, deletion and search time. For more look at Wikipedia

Simple Usage

package main

import (
	"fmt"
	"github.com/emin/skiplist"
)

func main(){
    // use string keys only
    list := skiplist.New(skiplist.StringComparator)
    list.Set("key-1", []byte("byte slice data"))
    list.Set("key-2", "string data")
    list.Set("key-3", 999)
    v := list.Get("key-2")
    fmt.Println(v)
    if list.Delete("key-2") {
        fmt.Println("key-2 is deleted")
    }
}

Iterating over skip list

package main

import (
	"fmt"
	"github.com/emin/skiplist"
)

func main(){
    // use int keys only
    list := skiplist.New(skiplist.IntComparator)
    list.Set(1, "data-1")
    list.Set(3, "data-3")
    list.Set(2, "data-2")
    
    it := list.Iterator()
    for it.Next() {
    	fmt.Printf("%v = %v \n", it.Key(), it.Value())
    }
}

For more examples, look at examples/ folder in the project.

Skiplist Interface

New(comparator func(interface{}, interface{}) int) *SkipList
Get(key interface{}) interface{}
Delete(key interface{}) bool
Set(key, value interface{})
KeyCount() int64
Iterator() Iterator

For more, look at

Benchmarks

Run on M1 Macbook Air 8GB model.

go test -bench=.
goos: darwin
goarch: arm64
pkg: github.com/emin/skiplist
BenchmarkSetString-8   	 1866468	       626.2 ns/op	     582 B/op	       5 allocs/op
BenchmarkSetInt-8      	 2842914	       438.2 ns/op	     559 B/op	       6 allocs/op
BenchmarkGetString-8   	 4044667	       277.7 ns/op	      16 B/op	       1 allocs/op
BenchmarkGetInt-8      	 8329945	       146.1 ns/op	       7 B/op	       0 allocs/op
BenchmarkGetHash-8     	24889994	        48.52 ns/op	       0 B/op	       0 allocs/op

At the last row BenchmarkGetHash-8 is map[string]string, I compared the numbers with hashtable performance while developing the code. Decided to left it as something to compare for you. Don't forget hashtable has O(1) access, skip list is O(log n).

License

MIT License