github.com/ethanzhuang/gofibonacciheap

Golang Fibonacci Heap

GoFibonacciHeap is a Golang implementation of Fibonacci Heap. This implementation is a bit different from the traditional Fibonacci Heap with an index map inside. Thanks to the index map, the internal struct 'node' no longer need to be exposed outsides the package. The index map also makes the random access to the values in the heap possible. But the union operation of this implementation is O(n) rather than O(1) of the traditional implementation.

Operations	Insert	Minimum	ExtractMin	Union	DecreaseKey	IncreaseKey	Delete	Get
Traditional Implementation	O(1)	O(1)	O(log n)¹	O(1)	O(1)¹	O(1)¹	O(log n)¹	N/A
This Implementation	O(1)	O(1)	O(log n)¹	O(n)	O(1)¹	O(1)¹	O(log n)¹	O(1)
¹ Amortized time.

##Requirements #####Download this package

go get github.com/starwander/GoFibonacciHeap

#####Implements Value interface of this package for all values going to be inserted by value interfaces

// Value is the interface that all values push into or pop from the FibHeap by value interfaces must implement.
type Value interface {
	// Tag returns the unique tag of the value.
	// The tag is used in the index map.
	Tag() interface{}
	// Key returns the key as known as the priority of the value.
	// The valid range of the key is (-inf, +inf].
	Key() float64
}

Supported Operations

• Interfaces use tag/key as inputs, treating heap as a priority queue only

• Insert: pushes the input tag/key into the heap.
• Minimum: returns the current minimum tag/key in the heap sorted by key.
• ExtractMin: returns the current minimum tag/key in the heap and then extracts them from the heap.
• DecreaseKey: decreases and updates the tag in the heap by the input key.
• IncreaseKey: increases and updates the tag in the heap by the input key.
• Delete: deletes the tag in the heap by the input.
• GetTag: searches and returns the tag/key in the heap by the input tag.
• ExtractTag: searches and extracts the tag/key in the heap by the input tag.

• Interfaces use value(Value interface) as inputs, treating heap as a priority queue and a value storage.

• InsertValue: pushes the input value into the heap.
• MinimumValue: returns the current minimum value in the heap sorted by key.
• ExtractMinValue: returns the current minimum value in the heap and then extracts the value from the heap.
• DecreaseKeyValue: decreases and updates the value in the heap by the input.
• IncreaseKeyValue: increases and updates the value in the heap by the input.
• DeleteValue: deletes the value in the heap by the input.
• GetValue: searches and returns the value in the heap by the input tag.
• ExtractValue: searches and extracts the value in the heap by the input tag.

• Common interfaces

• Union: merges the input heap in.
• Num: returns the current total number of values in the heap.
• String: provides some basic debug information of the heap.

Example

package main

import (
	"fmt"
	"github.com/starwander/GoFibonacciHeap"
)

type student struct {
	name string
	age  float64
}

func (s *student) Tag() interface{} {
	return s.name
}

func (s *student) Key() float64 {
	return s.age
}

func main() {
	heap := fibHeap.NewFibHeap()

	heap.InsertValue(&student{"John", 18.3})
	heap.InsertValue(&student{"Tom", 21.0})
	heap.InsertValue(&student{"Jessica", 19.4})
	heap.InsertValue(&student{"Amy", 23.1})

	fmt.Println(heap.Num())     // 4
	fmt.Println(heap.Minimum()) // &{John 18.3}
	fmt.Println(heap.Num())     // 4

	john := heap.GetValue("John")
	john.(*student).age = 20
	heap.IncreaseKeyValue(john)
	fmt.Println(heap.ExtractMin()) // &{Jessica 19.4}

	fmt.Println(heap.ExtractMin()) // &{John 20}
	fmt.Println(heap.Num())        // 2

	amy := heap.GetValue("Amy")
	amy.(*student).age = 16.5
	heap.DecreaseKeyValue(amy)
	fmt.Println(heap.ExtractMin()) // &{Amy 16.5}

	fmt.Println(heap.Num()) // 1
	fmt.Println(heap.ExtractValue("Tom")) // &{Tom 21}
	fmt.Println(heap.Num()) // 0
}

Reference

GoDoc

LICENSE

GoFibonacciHeap source code is licensed under the Apache Licence, Version 2.0.