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| 1 | +// Copyright 2021 gotomicro |
| 2 | +// |
| 3 | +// Licensed under the Apache License, Version 2.0 (the "License"); |
| 4 | +// you may not use this file except in compliance with the License. |
| 5 | +// You may obtain a copy of the License at |
| 6 | +// |
| 7 | +// http://www.apache.org/licenses/LICENSE-2.0 |
| 8 | +// |
| 9 | +// Unless required by applicable law or agreed to in writing, software |
| 10 | +// distributed under the License is distributed on an "AS IS" BASIS, |
| 11 | +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 12 | +// See the License for the specific language governing permissions and |
| 13 | +// limitations under the License. |
| 14 | + |
| 15 | +package queue |
| 16 | + |
| 17 | +import ( |
| 18 | + "errors" |
| 19 | + |
| 20 | + "github.com/gotomicro/ekit/internal/slice" |
| 21 | + |
| 22 | + "github.com/gotomicro/ekit" |
| 23 | +) |
| 24 | + |
| 25 | +var ( |
| 26 | + ErrOutOfCapacity = errors.New("ekit: 超出最大容量限制") |
| 27 | + ErrEmptyQueue = errors.New("ekit: 队列为空") |
| 28 | +) |
| 29 | + |
| 30 | +// PriorityQueue 是一个基于小顶堆的优先队列 |
| 31 | +// 当capacity <= 0时，为无界队列，切片容量会动态扩缩容 |
| 32 | +// 当capacity > 0 时，为有界队列，初始化后就固定容量，不会扩缩容 |
| 33 | +type PriorityQueue[T any] struct { |
| 34 | + // 用于比较前一个元素是否小于后一个元素 |
| 35 | + compare ekit.Comparator[T] |
| 36 | + // 队列容量 |
| 37 | + capacity int |
| 38 | + // 队列中的元素，为便于计算父子节点的index，0位置留空，根节点从1开始 |
| 39 | + data []T |
| 40 | +} |
| 41 | + |
| 42 | +func (p *PriorityQueue[T]) Len() int { |
| 43 | + return len(p.data) - 1 |
| 44 | +} |
| 45 | + |
| 46 | +// Cap 无界队列返回0，有界队列返回创建队列时设置的值 |
| 47 | +func (p *PriorityQueue[T]) Cap() int { |
| 48 | + return p.capacity |
| 49 | +} |
| 50 | + |
| 51 | +func (p *PriorityQueue[T]) IsBoundless() bool { |
| 52 | + return p.capacity <= 0 |
| 53 | +} |
| 54 | + |
| 55 | +func (p *PriorityQueue[T]) isFull() bool { |
| 56 | + return p.capacity > 0 && len(p.data)-1 == p.capacity |
| 57 | +} |
| 58 | + |
| 59 | +func (p *PriorityQueue[T]) isEmpty() bool { |
| 60 | + return len(p.data) < 2 |
| 61 | +} |
| 62 | + |
| 63 | +func (p *PriorityQueue[T]) Peek() (T, error) { |
| 64 | + if p.isEmpty() { |
| 65 | + var t T |
| 66 | + return t, ErrEmptyQueue |
| 67 | + } |
| 68 | + return p.data[1], nil |
| 69 | +} |
| 70 | + |
| 71 | +func (p *PriorityQueue[T]) Enqueue(t T) error { |
| 72 | + if p.isFull() { |
| 73 | + return ErrOutOfCapacity |
| 74 | + } |
| 75 | + |
| 76 | + p.data = append(p.data, t) |
| 77 | + node, parent := len(p.data)-1, (len(p.data)-1)/2 |
| 78 | + for parent > 0 && p.compare(p.data[node], p.data[parent]) < 0 { |
| 79 | + p.data[parent], p.data[node] = p.data[node], p.data[parent] |
| 80 | + node = parent |
| 81 | + parent = parent / 2 |
| 82 | + } |
| 83 | + |
| 84 | + return nil |
| 85 | +} |
| 86 | + |
| 87 | +func (p *PriorityQueue[T]) Dequeue() (T, error) { |
| 88 | + if p.isEmpty() { |
| 89 | + var t T |
| 90 | + return t, ErrEmptyQueue |
| 91 | + } |
| 92 | + |
| 93 | + pop := p.data[1] |
| 94 | + p.data[1] = p.data[len(p.data)-1] |
| 95 | + p.data = p.data[:len(p.data)-1] |
| 96 | + p.shrinkIfNecessary() |
| 97 | + p.heapify(p.data, len(p.data)-1, 1) |
| 98 | + return pop, nil |
| 99 | +} |
| 100 | + |
| 101 | +func (p *PriorityQueue[T]) shrinkIfNecessary() { |
| 102 | + if p.IsBoundless() { |
| 103 | + p.data = slice.Shrink[T](p.data) |
| 104 | + } |
| 105 | +} |
| 106 | + |
| 107 | +func (p *PriorityQueue[T]) heapify(data []T, n, i int) { |
| 108 | + minPos := i |
| 109 | + for { |
| 110 | + if left := i * 2; left <= n && p.compare(data[left], data[minPos]) < 0 { |
| 111 | + minPos = left |
| 112 | + } |
| 113 | + if right := i*2 + 1; right <= n && p.compare(data[right], data[minPos]) < 0 { |
| 114 | + minPos = right |
| 115 | + } |
| 116 | + if minPos == i { |
| 117 | + break |
| 118 | + } |
| 119 | + data[i], data[minPos] = data[minPos], data[i] |
| 120 | + i = minPos |
| 121 | + } |
| 122 | +} |
| 123 | + |
| 124 | +// NewPriorityQueue 创建优先队列 capacity <= 0 时，为无界队列，否则有有界队列 |
| 125 | +func NewPriorityQueue[T any](capacity int, compare ekit.Comparator[T]) *PriorityQueue[T] { |
| 126 | + sliceCap := capacity + 1 |
| 127 | + if capacity < 1 { |
| 128 | + capacity = 0 |
| 129 | + sliceCap = 64 |
| 130 | + } |
| 131 | + return &PriorityQueue[T]{ |
| 132 | + capacity: capacity, |
| 133 | + data: make([]T, 1, sliceCap), |
| 134 | + compare: compare, |
| 135 | + } |
| 136 | +} |
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