type Interface interface {
	sort.Interface
	Push(x any) // add x as element Len()
	Pop() any   // remove and return element Len() - 1.
}
// sort.Interface
type Interface interface {
    Len() int
    Less(i, j int) bool
    Swap(i, j int)
}

type myHeap []int

func (h *myHeap) Less(i, j int) bool {
	return (*h)[i] < (*h)[j]
}

func (h *myHeap) Swap(i, j int) {
	(*h)[i], (*h)[j] = (*h)[j], (*h)[i]
}

func (h *myHeap) Len() int {
	return len(*h)
}

// 把最后一個彈出，因為最小的值已經(jīng)被換到了最后
func (h *myHeap) Pop() (v any) {
	*h, v = (*h)[:h.Len()-1], (*h)[h.Len()-1]
	return
}

func (h *myHeap) Push(v any) {
	*h = append(*h, v.(int))
}

// 從小到大排序
func HeapSort(data []int) []int {
	hp := &myHeap{}
	for _, v := range data {
		heap.Push(hp, v)
	}
	heap.Init(hp)
	res := make([]int, hp.Len())
	for i := 0; hp.Len() > 0; i++ {
		res[i] = heap.Pop(hp).(int)
	}

	return res
}

// data = 6, 0, 1, 7, 9, 4, 3, 8, 2, 5
// hp 中存儲的是 0, 2, 1, 6, 5, 4, 3, 8, 7, 9

type Item struct {
	value    string
	priority int
	index    int
}
type PriorityQueue []*Item

func (pq PriorityQueue) Len() int { return len(pq) }

func (pq PriorityQueue) Less(i, j int) bool {
	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 any) {
	n := len(*pq)
	item := x.(*Item)
	item.index = n
	*pq = append(*pq, item)
}

func (pq *PriorityQueue) Pop() any {
	old := *pq
	n := len(old)
	item := old[n-1]
	old[n-1] = nil  // avoid memory leak
	item.index = -1 // for safety
	*pq = old[0 : n-1]
	return item
}

func (pq *PriorityQueue) update(item *Item, value string, priority int) {
	item.value = value
	item.priority = priority
	heap.Fix(pq, item.index)
}

func PriorityQueueTest() {
	items := map[string]int{
		"banana": 3, "apple": 2, "pear": 4,
	}

	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)

	item := &Item{
		value:    "orange",
		priority: 1,
	}
	heap.Push(&pq, item)
	pq.update(item, item.value, 5)

	for pq.Len() > 0 {
		item := heap.Pop(&pq).(*Item)
		fmt.Printf("%.2d:%s ", item.priority, item.value)
	}
}

type TimeSortedQueueItem struct {
	Time  int64
	Value interface{}
}

type TimeSortedQueue []*TimeSortedQueueItem

func (q TimeSortedQueue) Len() int           { return len(q) }
func (q TimeSortedQueue) Less(i, j int) bool { return q[i].Time < q[j].Time }
func (q TimeSortedQueue) Swap(i, j int)      { q[i], q[j] = q[j], q[i] }

func (q *TimeSortedQueue) Push(v interface{}) {
	*q = append(*q, v.(*TimeSortedQueueItem))
}

func (q *TimeSortedQueue) Pop() interface{} {
	n := len(*q)
	item := (*q)[n-1]
	*q = (*q)[0 : n-1]
	return item
}

func NewTimeSortedQueue(items ...*TimeSortedQueueItem) *TimeSortedQueue {
	q := make(TimeSortedQueue, len(items))
	for i, item := range items {
		q[i] = item
	}
	heap.Init(&q)
	return &q
}

func (q *TimeSortedQueue) PushItem(time int64, value interface{}) {
	heap.Push(q, &TimeSortedQueueItem{
		Time:  time,
		Value: value,
	})
}

func (q *TimeSortedQueue) PopItem() interface{} {
	if q.Len() == 0 {
		return nil
	}

	return heap.Pop(q).(*TimeSortedQueueItem).Value
}