priority_queue_with_sorted_array.go

package main

import (
	"fmt"
)

type QueueElement struct {
	value    interface{}
	priority int
}

type PriorityQueue struct {
	maxSize int
	data    []QueueElement
	size    int
}

//...
func main() {
	pq := PriorityQueue{}
	pq.SetMaxSize(10)
	pq.Enqueue(1, 5)
	pq.Enqueue(5, 2)
	pq.Enqueue(6, 3)
	pq.Enqueue(10, 1)
	pq.Enqueue(8, 2)

	pq.Display()              //Returns [10,5,8,6,1]
	fmt.Println(pq.Dequeue()) //Returns {10 1}
	fmt.Println(pq.Dequeue()) //Returns {5 2}
	fmt.Println(pq.Dequeue()) //Returns {8 2}
	fmt.Println(pq.Peek())    //Returns {6 3}
	pq.Display()              //Displays [6,1]
}

// Sets the max-size of the priority queue
func (p *PriorityQueue) SetMaxSize(maxSize int) {
	p.maxSize = maxSize
}

// Checks if the priority queue is empty
func (p *PriorityQueue) IsEmpty() bool {
	return p.size == 0
}

// Adds a new element to the priority queue in its exact location
func (p *PriorityQueue) Enqueue(el interface{}, priority int) {
	newElement := QueueElement{el, priority}
	if p.size == p.maxSize {
		panic("Queue has reached its max size limit.")
	}

	if p.IsEmpty() {
		p.data = append(p.data, newElement)
		p.size++
		return
	}

	p.data = append(p.data, newElement)
	i := p.size - 1
	for i >= 0 {
		if p.data[i].priority > priority {
			p.data[i+1] = p.data[i]
			i--
		} else {
			break
		}
	}
	p.data[i+1] = newElement
	p.size++
}

// Returns and Removes the first element of the priority queue
func (p *PriorityQueue) Dequeue() QueueElement {
	if p.IsEmpty() {
		panic("Queue is empty.")
	}
	dequeued := p.data[0]

	p.data = p.data[1:]
	p.size--
	return dequeued
}

// Returns the first element in the queue without modifying the queue
func (p *PriorityQueue) Peek() interface{} {
	if p.IsEmpty() {
		panic("Queue is empty.")
	}

	return p.data[0]
}

// Display the elements of the queue in an array form
func (p *PriorityQueue) Display() {
	if p.IsEmpty() {
		panic("Queue is empty.")
	}

	arr := make([]interface{}, p.size)
	i := 0
	for i < p.size {
		arr[i] = p.data[i].value
		i++
	}
	fmt.Println("Priority Queue elements: ", arr)
}