import (
	"container/heap"
	"fmt"
)

type IntHeap []int

func main() {
	h := &IntHeap{2, 1, 5, 6, 4, 3, 7, 9, 8, 0} // 创建slice
	heap.Init(h)                                // 将数组切片进行堆化
	fmt.Println(*h)                             // [0 1 3 6 2 5 7 9 8 4] 由Less方法可控制小顶堆
	fmt.Println(heap.Pop(h))                    // 调用pop 0 返回移除的顶部最小元素
	heap.Push(h, 6)                             // 调用push [1 2 3 6 4 5 7 9 8] 添加一个元素进入堆中进行堆化
	fmt.Println("new: ", *h)                    // [1 2 3 6 4 5 7 9 8 6]
	for len(*h) > 0 {                           // 持续推出顶部最小元素
		fmt.Printf("%d \n ", heap.Pop(h))
	}
}

func (h IntHeap) Len() int { return len(h) }

func (h IntHeap) Less(i, j int) bool { return h[i] < h[j] } // 这里决定 大小顶堆 现在是小顶堆

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

func (h *IntHeap) Pop() interface{} {
	old := *h
	n := len(old)
	fmt.Println("old: ", old) // [1 2 3 6 4 5 7 9 8 0] 将顶小堆元素与最后一个元素交换位置，在进行堆排序的结果

	x := old[n-1]
	*h = old[0 : n-1]
	fmt.Println(*h) // [1 2 3 6 4 5 7 9 8]
	return x
}

func (h *IntHeap) Push(x interface{}) { // 绑定push方法，插入新元素
	*h = append(*h, x.(int))
}

// The Interface type describes the requirements
// for a type using the routines in this package.
// Any type that implements it may be used as a
// min-heap with the following invariants (established after
// Init has been called or if the data is empty or sorted):
//
//	!h.Less(j, i) for 0 <= i < h.Len() and 2*i+1 <= j <= 2*i+2 and j < h.Len()
//
// Note that Push and Pop in this interface are for package heap's
// implementation to call. To add and remove things from the heap,
// use heap.Push and heap.Pop.
type Interface interface { // 该接口组合了另外的sort.Interface接口，所以也要实现里面的方法
	sort.Interface
	Push(x interface{}) // add x as element Len()
	Pop() interface{}   // remove and return element Len() - 1.
}

// Init establishes the heap invariants required by the other routines in this package.
// Init is idempotent with respect to the heap invariants
// and may be called whenever the heap invariants may have been invalidated.
// The complexity is O(n) where n = h.Len().
func Init(h Interface) {
	// heapify
	n := h.Len()
	for i := n/2 - 1; i >= 0; i-- {
		down(h, i, n)
	}
}

package sort

// A type, typically a collection, that satisfies sort.Interface can be
// sorted by the routines in this package. The methods require that the
// elements of the collection be enumerated by an integer index.
type Interface interface {
	// Len is the number of elements in the collection.
	Len() int
	// Less reports whether the element with
	// index i should sort before the element with index j.
	Less(i, j int) bool
	// Swap swaps the elements with indexes i and j.
	Swap(i, j int)
}

// Push pushes the element x onto the heap.
// The complexity is O(log n) where n = h.Len().
func Push(h Interface, x interface{}) {
	h.Push(x)
	up(h, h.Len()-1)
}

// Pop removes and returns the minimum element (according to Less) from the heap.
// The complexity is O(log n) where n = h.Len().
// Pop is equivalent to Remove(h, 0).
func Pop(h Interface) interface{} {
	n := h.Len() - 1
	h.Swap(0, n)
	down(h, 0, n)
	return h.Pop()
}

// Remove removes and returns the element at index i from the heap.
// The complexity is O(log n) where n = h.Len().
func Remove(h Interface, i int) interface{} {
	n := h.Len() - 1
	if n != i {
		h.Swap(i, n)
		if !down(h, i, n) {
			up(h, i)
		}
	}
	return h.Pop()
}

// Fix re-establishes the heap ordering after the element at index i has changed its value.
// Changing the value of the element at index i and then calling Fix is equivalent to,
// but less expensive than, calling Remove(h, i) followed by a Push of the new value.
// The complexity is O(log n) where n = h.Len().
func Fix(h Interface, i int) {
	if !down(h, i, h.Len()) {
		up(h, i)
	}
}

func up(h Interface, j int) {
	for {
		i := (j - 1) / 2 // parent
		if i == j || !h.Less(j, i) {
			break
		}
		h.Swap(i, j)
		j = i
	}
}

func down(h Interface, i0, n int) bool {
	i := i0
	for {
		j1 := 2*i + 1
		if j1 >= n || j1 < 0 { // j1 < 0 after int overflow
			break
		}
		j := j1 // left child
		if j2 := j1 + 1; j2 < n && h.Less(j2, j1) {
			j = j2 // = 2*i + 2  // right child
		}
		if !h.Less(j, i) {
			break
		}
		h.Swap(i, j)
		i = j
	}
	return i > i0
}

h := &IntHeap{3, 8, 6}  // 创建IntHeap类型的原始数据
func Init(h Interface)  // 对heap进行初始化，生成小根堆（或大根堆）
func Push(h Interface, x interface{})  // 往堆里面插入内容
func Pop(h Interface) interface{}  // 从堆顶pop出内容
func Remove(h Interface, i int) interface{}  // 从指定位置删除数据，并返回删除的数据
func Fix(h Interface, i int)  // 从i位置数据发生改变后，对堆再平衡，优先级队列使用到了该方法

import (
    "container/heap"
    "fmt"
)

type Item struct {
    value    string // 优先级队列中的数据，可以是任意类型，这里使用string
    priority int    // 优先级队列中节点的优先级
    index    int    // index是该节点在堆中的位置
}

// 优先级队列需要实现heap的interface
type PriorityQueue []*Item

// 绑定Len方法
func (pq PriorityQueue) Len() int {
    return len(pq)
}

// 绑定Less方法，这里用的是小于号，生成的是小根堆
func (pq PriorityQueue) Less(i, j int) bool {
    return pq[i].priority < pq[j].priority
}

// 绑定swap方法
func (pq PriorityQueue) Swap(i, j int) {
    pq[i], pq[j] = pq[j], pq[i]
    pq[i].index, pq[j].index = i, j
}

// 绑定put方法，将index置为-1是为了标识该数据已经出了优先级队列了
func (pq *PriorityQueue) Pop() interface{} {
    old := *pq
    n := len(old)
    item := old[n-1]
    *pq = old[0 : n-1]
    item.index = -1
    return item
}

// 绑定push方法
func (pq *PriorityQueue) Push(x interface{}) {
    n := len(*pq)
    item := x.(*Item)
    item.index = n
    *pq = append(*pq, item)
}

// 更新修改了优先级和值的item在优先级队列中的位置
func (pq *PriorityQueue) update(item *Item, value string, priority int) {
    item.value = value
    item.priority = priority
    heap.Fix(pq, item.index)
}

func main() {
    // 创建节点并设计他们的优先级
    items := map[string]int{"二毛": 5, "张三": 3, "狗蛋": 9}
    i := 0
    pq := make(PriorityQueue, len(items)) // 创建优先级队列，并初始化
    for k, v := range items {             // 将节点放到优先级队列中
        pq[i] = &Item{
            value:    k,
            priority: v,
            index:    i}
        i++
    }
    heap.Init(&pq) // 初始化堆
    item := &Item{ // 创建一个item
        value:    "李四",
        priority: 1,
    }
    heap.Push(&pq, item)           // 入优先级队列
    pq.update(item, item.value, 6) // 更新item的优先级
    for len(pq) > 0 {
        item := heap.Pop(&pq).(*Item)
        fmt.Printf("%.2d:%s index:%.2d\n", item.priority, item.value, item.index)
    }
}

输出结果：
03:张三 index:-01
05:二毛 index:-01
06:李四 index:-01
09:狗蛋 index:-01