github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/container/heap/heap_test.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package heap

import (
	"math/rand"
	"testing"
)

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)
}

// push 和 pop 都是操作的最后一个元素
func (h *myHeap) Pop() (v interface{}) {
	// Pop 删除并返回最后一个元素， 并且更新heap 为前h.Len()-1的元素数组
	*h, v = (*h)[:h.Len()-1], (*h)[h.Len()-1]
	return
}

// Push 是从数组后面添加元素
func (h *myHeap) Push(v interface{}) {
	*h = append(*h, v.(int))
}

func (h myHeap) verify(t *testing.T, i int) {
	t.Helper()
	n := h.Len()
	j1 := 2*i + 1
	j2 := 2*i + 2
	if j1 < n { // 存在左子树节点
		if h.Less(j1, i) { // 如果左节点小于i节点，表示 子节点小于父节点值， 不满足最小堆
			t.Errorf("heap invariant invalidated [%d] = %d > [%d] = %d", i, h[i], j1, h[j1])
			return
		}
		h.verify(t, j1)
	}
	if j2 < n { // 存在右子树节点
		if h.Less(j2, i) {
			t.Errorf("heap invariant invalidated [%d] = %d > [%d] = %d", i, h[i], j1, h[j2])
			return
		}
		h.verify(t, j2)
	}
}

func TestInit0(t *testing.T) {
	h := new(myHeap) // 初始化
	// 装填数据
	for i := 20; i > 0; i-- {
		h.Push(0) // all elements are the same
	}
	Init(h)        // 构建最小堆
	h.verify(t, 0) // 验证最小堆

	// 出去值 并验证最小堆
	for i := 1; h.Len() > 0; i++ {
		x := Pop(h).(int)
		h.verify(t, 0)
		if x != 0 {
			t.Errorf("%d.th pop got %d; want %d", i, x, 0)
		}
	}
}

func TestInit1(t *testing.T) {
	h := new(myHeap)
	for i := 20; i > 0; i-- {
		h.Push(i) // all elements are different
	}
	Init(h)
	h.verify(t, 0)

	for i := 1; h.Len() > 0; i++ {
		x := Pop(h).(int)
		h.verify(t, 0)
		if x != i {
			t.Errorf("%d.th pop got %d; want %d", i, x, i)
		}
	}
}

func Test(t *testing.T) {
	h := new(myHeap) // 初始化一个空数组
	h.verify(t, 0)   // 堆化验证

	for i := 20; i > 10; i-- {
		h.Push(i)
	}
	Init(h)
	h.verify(t, 0)

	for i := 10; i > 0; i-- {
		Push(h, i)
		h.verify(t, 0)
	}

	for i := 1; h.Len() > 0; i++ {
		x := Pop(h).(int)
		if i < 20 {
			Push(h, 20+i)
		}
		h.verify(t, 0)
		if x != i {
			t.Errorf("%d.th pop got %d; want %d", i, x, i)
		}
	}
}

func TestRemove0(t *testing.T) {
	h := new(myHeap)
	for i := 0; i < 10; i++ {
		h.Push(i)
	}
	h.verify(t, 0)

	for h.Len() > 0 {
		i := h.Len() - 1
		x := Remove(h, i).(int) // 删除第i位 堆化调整最小堆
		if x != i {
			t.Errorf("Remove(%d) got %d; want %d", i, x, i)
		}
		h.verify(t, 0)
	}
}

func TestRemove1(t *testing.T) {
	h := new(myHeap)
	for i := 0; i < 10; i++ {
		h.Push(i)
	}
	h.verify(t, 0)

	for i := 0; h.Len() > 0; i++ {
		x := Remove(h, 0).(int) // 每次都是删除堆顶调整最小堆
		if x != i {
			t.Errorf("Remove(0) got %d; want %d", x, i)
		}
		h.verify(t, 0)
	}
}

func TestRemove2(t *testing.T) {
	N := 10

	h := new(myHeap)
	for i := 0; i < N; i++ {
		h.Push(i)
	}
	h.verify(t, 0)

	m := make(map[int]bool)
	for h.Len() > 0 {
		m[Remove(h, (h.Len()-1)/2).(int)] = true
		h.verify(t, 0)
	}

	if len(m) != N {
		t.Errorf("len(m) = %d; want %d", len(m), N)
	}
	for i := 0; i < len(m); i++ {
		if !m[i] {
			t.Errorf("m[%d] doesn't exist", i)
		}
	}
}

func BenchmarkDup(b *testing.B) {
	const n = 10000
	h := make(myHeap, 0, n)
	for i := 0; i < b.N; i++ {
		for j := 0; j < n; j++ {
			Push(&h, 0) // all elements are the same
		}
		for h.Len() > 0 {
			Pop(&h)
		}
	}
}

func TestFix(t *testing.T) { // 测试修复值之后 堆化调整最小堆， 这个比删除这个值 再插入一个新元素效率更高
	h := new(myHeap)
	h.verify(t, 0)

	for i := 200; i > 0; i -= 10 {
		Push(h, i)
	}
	h.verify(t, 0)

	if (*h)[0] != 10 {
		t.Fatalf("Expected head to be 10, was %d", (*h)[0])
	}
	(*h)[0] = 210 // 修改堆顶元素
	Fix(h, 0)     // 调整堆顶0 位置， 堆化最小堆
	h.verify(t, 0)

	for i := 100; i > 0; i-- {
		elem := rand.Intn(h.Len()) // 随机调整，随机堆化并验证
		if i&1 == 0 {
			(*h)[elem] *= 2
		} else {
			(*h)[elem] /= 2
		}
		Fix(h, elem)
		h.verify(t, 0)
	}
}