1// Copyright 2012 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// This example demonstrates an integer heap built using the heap interface.
6package heap_test
7
8import (
9	"container/heap"
10	"fmt"
11)
12
13// An IntHeap is a min-heap of ints.
14type IntHeap []int
15
16func (h IntHeap) Len() int           { return len(h) }
17func (h IntHeap) Less(i, j int) bool { return h[i] < h[j] }
18func (h IntHeap) Swap(i, j int)      { h[i], h[j] = h[j], h[i] }
19
20func (h *IntHeap) Push(x any) {
21	// Push and Pop use pointer receivers because they modify the slice's length,
22	// not just its contents.
23	*h = append(*h, x.(int))
24}
25
26func (h *IntHeap) Pop() any {
27	old := *h
28	n := len(old)
29	x := old[n-1]
30	*h = old[0 : n-1]
31	return x
32}
33
34// This example inserts several ints into an IntHeap, checks the minimum,
35// and removes them in order of priority.
36func Example_intHeap() {
37	h := &IntHeap{2, 1, 5}
38	heap.Init(h)
39	heap.Push(h, 3)
40	fmt.Printf("minimum: %d\n", (*h)[0])
41	for h.Len() > 0 {
42		fmt.Printf("%d ", heap.Pop(h))
43	}
44	// Output:
45	// minimum: 1
46	// 1 2 3 5
47}
48