go标准库——优先级队列的实现
package heap_test
// priorty_queue是以个带权值观念的queue，它允许加入新元素，移除旧元素，审视元素值等功能
import (
"container/heap"
"fmt"
"testing"
)
// Item 是我们在优先队列中管理的东西
type Item struct {
value string // The value of the item; arbitrary.
priority int // 队列中项目的优先级
// The index is needed by update and is maintained by the methods.
index int //在堆中的索引
}
// 优先级队列
type PriorityQueue []*Item
func (pq PriorityQueue) Len() int { return len(pq) }
func (pq PriorityQueue) Less(i, j int) bool {
// 我们希望 Pop 给我们最高而不是最低的优先级，所以我们使用比这里更大的优先级。
return pq[i].priority > pq[j].priority
}
func (pq PriorityQueue) Swap(i, j int) {
pq[i], pq[j] = pq[j], pq[i]
pq[i].index = i
pq[j].index = j
}
func (pq *PriorityQueue) Push(x interface{}) {
n := len(*pq)
item := x.(*Item)
item.index = n
*pq = append(*pq, item)
}
func (pq *PriorityQueue) Pop() interface{} {
old := *pq
n := len(old)
item := old[n-1]
old[n-1] = nil // 避免内存泄漏
item.index = -1 // 为了安全
*pq = old[0 : n-1]
return item
}
// update 修改队列中项目的优先级和值。
func (pq *PriorityQueue) update(item *Item, value string, priority int) {
item.value = value
item.priority = priority
heap.Fix(pq, item.index)
}
// This example creates a PriorityQueue with some items, adds and manipulates an item,
// and then removes the items in priority order.
func Test_priorityQueue(t *testing.T) {
// Some items and their priorities.
items := map[string]int{
"banana": 3, "apple": 2, "pear": 4,
}
// Create a priority queue, put the items in it, and
// establish the priority queue (heap) invariants.
pq := make(PriorityQueue, len(items))
i := 0
for value, priority := range items {
pq[i] = &Item{
value: value,
priority: priority,
index: i,
}
i++
}
heap.Init(&pq)
// 插入一个新项目，然后修改其优先级.
item := &Item{
value: "orange",
priority: 1,
}
heap.Push(&pq, item)
pq.update(item, item.value, 5)
// Take the items out; they arrive in decreasing priority order.
for pq.Len() > 0 {
item := heap.Pop(&pq).(*Item)
fmt.Printf("%.2d:%s ", item.priority, item.value)
}
// Output:
// 05:orange 04:pear 03:banana 02:apple
}