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priority_queue.go
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priority_queue.go
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// The MIT License
//
// Copyright (c) 2020 Temporal Technologies Inc. All rights reserved.
//
// Copyright (c) 2020 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package collection
import (
"container/heap"
)
type (
priorityQueueImpl[T any] struct {
compareLess func(this T, other T) bool
items []T
}
)
// NewPriorityQueue create a new priority queue
func NewPriorityQueue[T any](
compareLess func(this T, other T) bool,
) Queue[T] {
return &priorityQueueImpl[T]{
compareLess: compareLess,
}
}
// NewPriorityQueueWithItems creats a new priority queue
// with the provided list of items.
// PriorityQueue will take ownership of the passed in items,
// so caller should stop modifying it.
// The complexity is O(n) where n is the number of items
func NewPriorityQueueWithItems[T any](
compareLess func(this T, other T) bool,
items []T,
) Queue[T] {
pq := &priorityQueueImpl[T]{
compareLess: compareLess,
items: items,
}
heap.Init(pq)
return pq
}
// Peek returns the top item of the priority queue
func (pq *priorityQueueImpl[T]) Peek() T {
if pq.IsEmpty() {
panic("Cannot peek item because priority queue is empty")
}
return pq.items[0]
}
// Add push an item to priority queue
func (pq *priorityQueueImpl[T]) Add(item T) {
heap.Push(pq, item)
}
// Remove pop an item from priority queue
func (pq *priorityQueueImpl[T]) Remove() T {
return heap.Pop(pq).(T)
}
// IsEmpty indicate if the priority queue is empty
func (pq *priorityQueueImpl[T]) IsEmpty() bool {
return pq.Len() == 0
}
// below are the functions used by heap.Interface and go internal heap implementation
// Len implements sort.Interface
func (pq *priorityQueueImpl[T]) Len() int {
return len(pq.items)
}
// Less implements sort.Interface
func (pq *priorityQueueImpl[T]) Less(i, j int) bool {
return pq.compareLess(pq.items[i], pq.items[j])
}
// Swap implements sort.Interface
func (pq *priorityQueueImpl[T]) Swap(i, j int) {
pq.items[i], pq.items[j] = pq.items[j], pq.items[i]
}
// Push push an item to priority queue, used by go internal heap implementation
func (pq *priorityQueueImpl[T]) Push(item interface{}) {
pq.items = append(pq.items, item.(T))
}
// Pop pop an item from priority queue, used by go internal heap implementation
func (pq *priorityQueueImpl[T]) Pop() interface{} {
pqItem := pq.items[pq.Len()-1]
pq.items = pq.items[0 : pq.Len()-1]
return pqItem
}