GO中的优先队列

Question

can anyone explain me this thing: I want implement priority queue in GO (interface implementation got from link, but for lowest)

My code:

pq := make(PriorityQueue, 0)

pq.Push(&Item{value: 0, priority: 0})

heap.Init(&pq)

fmt.Println(heap.Pop(&pq).(*Item))

item := &Item{value: 1, priority: 10}
pq.Push(item)
item = &Item{value: 2, priority: 20}
pq.Push(item)
item = &Item{value: 3, priority: 5}
pq.Push(item)

fmt.Println(heap.Pop(&pq).(*Item))
fmt.Println(heap.Pop(&pq).(*Item))
fmt.Println(heap.Pop(&pq).(*Item))

// Output:
&{0 0 -1}
&{1 10 -1}
&{3 5 -1}
&{2 20 -1}

Why it not outputs:

&{0 0 -1}
&{3 5 -1} 
...

Answer 1

The way this particular priority queue is implemented, you should call heap.Init after you've pushed your items into the queue, as the original example demonstrates.

pq := make(PriorityQueue, 0)

pq.Push(&Item{value: "0", priority: 0, index: 0})
item := &Item{value: "1", priority: 10, index: 1}
pq.Push(item)
item = &Item{value: "2", priority: 20, index: 2}
pq.Push(item)
item = &Item{value: "3", priority: 5, index: 3}
pq.Push(item)

heap.Init(&pq)

fmt.Println(heap.Pop(&pq).(*Item))
fmt.Println(heap.Pop(&pq).(*Item))
fmt.Println(heap.Pop(&pq).(*Item))
fmt.Println(heap.Pop(&pq).(*Item))

Will print the items in priority order, as expected.