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87 lines
2.6 KiB
Go
87 lines
2.6 KiB
Go
// Copyright (c) 2015, Emir Pasic. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package priorityqueue implements a priority queue backed by binary queue.
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//
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// An unbounded priority queue based on a priority queue.
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// The elements of the priority queue are ordered by a comparator provided at queue construction time.
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//
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// The heap of this queue is the least/smallest element with respect to the specified ordering.
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// If multiple elements are tied for least value, the heap is one of those elements arbitrarily.
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//
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// Structure is not thread safe.
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//
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// References: https://en.wikipedia.org/wiki/Priority_queue
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package priorityqueue
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import (
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"fmt"
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"github.com/emirpasic/gods/queues"
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"github.com/emirpasic/gods/trees/binaryheap"
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"github.com/emirpasic/gods/utils"
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"strings"
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)
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// Assert Queue implementation
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var _ queues.Queue = (*Queue)(nil)
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// Queue holds elements in an array-list
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type Queue struct {
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heap *binaryheap.Heap
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Comparator utils.Comparator
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}
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// NewWith instantiates a new empty queue with the custom comparator.
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func NewWith(comparator utils.Comparator) *Queue {
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return &Queue{heap: binaryheap.NewWith(comparator), Comparator: comparator}
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}
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// Enqueue adds a value to the end of the queue
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func (queue *Queue) Enqueue(value interface{}) {
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queue.heap.Push(value)
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}
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// Dequeue removes first element of the queue and returns it, or nil if queue is empty.
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// Second return parameter is true, unless the queue was empty and there was nothing to dequeue.
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func (queue *Queue) Dequeue() (value interface{}, ok bool) {
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return queue.heap.Pop()
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}
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// Peek returns top element on the queue without removing it, or nil if queue is empty.
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// Second return parameter is true, unless the queue was empty and there was nothing to peek.
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func (queue *Queue) Peek() (value interface{}, ok bool) {
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return queue.heap.Peek()
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}
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// Empty returns true if queue does not contain any elements.
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func (queue *Queue) Empty() bool {
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return queue.heap.Empty()
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}
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// Size returns number of elements within the queue.
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func (queue *Queue) Size() int {
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return queue.heap.Size()
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}
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// Clear removes all elements from the queue.
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func (queue *Queue) Clear() {
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queue.heap.Clear()
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}
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// Values returns all elements in the queue.
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func (queue *Queue) Values() []interface{} {
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return queue.heap.Values()
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}
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// String returns a string representation of container
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func (queue *Queue) String() string {
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str := "PriorityQueue\n"
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values := make([]string, queue.heap.Size(), queue.heap.Size())
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for index, value := range queue.heap.Values() {
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values[index] = fmt.Sprintf("%v", value)
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}
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str += strings.Join(values, ", ")
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return str
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}
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