examples/priorityqueue/priorityqueue.go

// Copyright (c) 2015, Emir Pasic. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package main

import (
	pq "github.com/emirpasic/gods/queues/priorityqueue"
	"github.com/emirpasic/gods/utils"
)

// Element is an entry in the priority queue
type Element struct {
	name     string
	priority int
}

// Comparator function (sort by element's priority value in descending order)
func byPriority(a, b interface{}) int {
	priorityA := a.(Element).priority
	priorityB := b.(Element).priority
	return -utils.IntComparator(priorityA, priorityB) // "-" descending order
}

// PriorityQueueExample to demonstrate basic usage of BinaryHeap
func main() {
	a := Element{name: "a", priority: 1}
	b := Element{name: "b", priority: 2}
	c := Element{name: "c", priority: 3}

	queue := pq.NewWith(byPriority) // empty
	queue.Enqueue(a)                // {a 1}
	queue.Enqueue(c)                // {c 3}, {a 1}
	queue.Enqueue(b)                // {c 3}, {b 2}, {a 1}
	_ = queue.Values()              // [{c 3} {b 2} {a 1}]
	_, _ = queue.Peek()             // {c 3} true
	_, _ = queue.Dequeue()          // {c 3} true
	_, _ = queue.Dequeue()          // {b 2} true
	_, _ = queue.Dequeue()          // {a 1} true
	_, _ = queue.Dequeue()          // <nil> false (nothing to dequeue)
	queue.Clear()                   // empty
	_ = queue.Empty()               // true
	_ = queue.Size()                // 0
}