我是 Go 的新手,已经实现了一个二叉搜索树。该树可以存储任何值(具体来说,任何实现 interface{}
的值)。
我想在此实现的基础上创建一个自平衡的红黑树。在面向对象的语言中,我会定义一个 BinarySearchTree
的子类,它添加一个 color
数据成员,然后覆盖 Insert
方法来执行平衡操作。
问题:如何在不重复代码的情况下用 Go 实现二叉搜索树和红黑树?
当前的二叉搜索树实现
这是我的二叉搜索树实现:
package trees
import (
"github.com/modocache/cargo/comparators"
"reflect"
)
type BinarySearchTree struct {
Parent *BinarySearchTree
Left *BinarySearchTree
Right *BinarySearchTree
Value interface{} // Can hold any value
less comparators.Less // A comparator function to determine whether
// an inserted value is placed left or right
}
func NewBinarySearchTree(value interface{}, less comparators.Less) *BinarySearchTree {
return &BinarySearchTree{Value: value, less: less}
}
func (tree *BinarySearchTree) Insert(value interface{}) *BinarySearchTree {
if tree.less(value, tree.Value) {
return tree.insertLeft(value)
} else {
return tree.insertRight(value)
}
}
func (tree *BinarySearchTree) insertLeft(value interface{}) *BinarySearchTree {
if tree.Left == nil {
tree.Left = &BinarySearchTree{Value: value, Parent: tree, less: tree.less}
return tree.Left
} else {
return tree.Left.Insert(value)
}
}
func (tree *BinarySearchTree) insertRight(value interface{}) *BinarySearchTree {
if tree.Right == nil {
tree.Right = &BinarySearchTree{Value: value, Parent: tree, less: tree.less}
return tree.Right
} else {
return tree.Right.Insert(value)
}
}
func (tree *BinarySearchTree) Find(value interface{}) *BinarySearchTree {
if reflect.DeepEqual(value, tree.Value) {
return tree
} else if tree.less(value, tree.Value) {
return tree.findLeft(value)
} else {
return tree.findRight(value)
}
}
func (tree *BinarySearchTree) findLeft(value interface{}) *BinarySearchTree {
if tree.Left == nil {
return nil
} else {
return tree.Left.Find(value)
}
}
func (tree *BinarySearchTree) findRight(value interface{}) *BinarySearchTree {
if tree.Right == nil {
return nil
} else {
return tree.Right.Find(value)
}
}
这是一个如何使用这个结构的例子:
tree := NewBinarySearchTree(100, func(value, treeValue interface{}) bool {
return value.(int) < treeValue.(int)
})
tree.Insert(200)
tree.Insert(300)
tree.Insert(250)
tree.Insert(150)
tree.Insert(275)
tree.Find(250) // Returns tree.Right.Right.Left
期望的(但不可能的)红黑树实现
我想像这样“扩展”BinarySearchTree
struct
:
type RedBlackTree struct {
Parent *RedBlackTree // These must be able to store
Left *RedBlackTree // pointers to red-black trees
Right *RedBlackTree
Value interface{}
less comparators.Less
color RedBlackTreeColor // Each tree must maintain a color property
}
然后像这样“覆盖”.Insert()
方法:
func (tree *RedBlackTree) Insert(value interface{}) *RedBlackTree {
var inserted *RedBlackTree
// Insertion logic is identical to BinarySearchTree
if tree.less(value, tree.Value) {
inserted = tree.insertLeft(value)
} else {
inserted tree.insertRight(value)
}
// .balance() is a private method on RedBlackTree that balances
// the tree based on each node's color
inserted.balance()
// Returns a *RedBlackTree
return inserted
}
不过,我认为这不是惯用的 Go 代码。
- 由于
BinarySearchTree
是用指向其他BinarySearchTree
结构的指针定义的,因此“扩展”BinarySearchTree
的RedBlackTree
仍然有指向BinarySearchTree
对象的指针。 - 无法“覆盖”
.Insert()
。我唯一的选择是定义另一种方法,例如.BalancedInsert()
。
正在尝试
我目前正在尝试的一个想法是定义一个这样的接口(interface):
type BinarySearchable interface {
Parent() *BinarySearchable
SetParent(searchable *BinarySearchable)
Left() *BinarySearchable
SetLeft(searchable *BinarySearchable)
Right() *BinarySearchable
SetRight(searchable *BinarySearchable)
Value() interface{}
Less() comparators.Less
Insert(searchable *BinarySearchable) *BinarySearchable
Find(value interface{}) *BinarySearchable
}
BinarySearchTree
和 RedBlackTree
将实现这些接口(interface)。然而,一个问题是如何共享 .Insert()
逻辑。也许定义每个结构将使用的私有(private)函数?
欢迎提出任何建议。
最佳答案
这是我想出来的。我宁愿接受另一个答案,但这是迄今为止最好的答案。
BinarySearchable
接口(interface)
BinarySearchTree
和RedBlackTree
都符合这个接口(interface)。该文件还定义了所有二进制可搜索结构共有的函数,包括 insert()
、.find()
、leftRotate()
等上。
为了动态创建各种类型的对象,insert()
函数接受一个childConstructor
函数参数。 BinarySearchTree
和 RedBlackTree
使用此函数创建任意类型的子树。
// binary_searchable.go
type BinarySearchable interface {
Parent() BinarySearchable
SetParent(searchable BinarySearchable)
Left() BinarySearchable
SetLeft(searchable BinarySearchable)
Right() BinarySearchable
SetRight(searchable BinarySearchable)
Value() interface{}
Insert(value interface{}) BinarySearchable
Find(value interface{}) BinarySearchable
Less() comparators.Less
}
type childConstructor func(parent BinarySearchable, value interface{}) BinarySearchable
func insert(searchable BinarySearchable, value interface{}, constructor childConstructor) BinarySearchable {
if searchable.Less()(value, searchable.Value()) {
if searchable.Left() == nil {
// The constructor function is used to
// create children of dynamic types
searchable.SetLeft(constructor(searchable, value))
return searchable.Left()
} else {
return searchable.Left().Insert(value)
}
} else {
if searchable.Right() == nil {
searchable.SetRight(constructor(searchable, value))
return searchable.Right()
} else {
return searchable.Right().Insert(value)
}
}
}
二叉搜索树
这是嵌入在其他树结构中的“基础”结构。它提供了 BinarySearchable
接口(interface)方法的默认实现,以及每棵树将用于存储其子树的数据属性。
// binary_search_tree.go
type BinarySearchTree struct {
parent BinarySearchable
left BinarySearchable
right BinarySearchable
value interface{}
less comparators.Less
}
func (tree *BinarySearchTree) Parent() BinarySearchable {
return tree.parent
}
func (tree *BinarySearchTree) SetParent(parent BinarySearchable) {
tree.parent = parent
}
// ...setters and getters for left, right, value, less, etc.
func (tree *BinarySearchTree) Insert(value interface{}) BinarySearchable {
// Pass `insert()` a constructor that creates a `*BinarySearchTree`
constructor := func(parent BinarySearchable, value interface{}) BinarySearchable {
return &BinarySearchTree{value: value, less: tree.less, parent: parent}
}
return insert(tree, value, constructor).(*BinarySearchTree)
}
func (tree *BinarySearchTree) Find(value interface{}) BinarySearchable {
return find(tree, value)
}
红黑树
这嵌入了 BinarySearchTree
并将自定义构造函数传递给 insert()
。为简洁起见,省略了平衡代码;你可以see the whole file here .
// red_black_tree.go
type RedBlackTree struct {
*BinarySearchTree
color RedBlackTreeColor
}
func NewRedBlackTree(value interface{}, less comparators.Less) *RedBlackTree {
return &RedBlackTree{&BinarySearchTree{value: value, less: less}, Black}
}
func (tree *RedBlackTree) Insert(value interface{}) BinarySearchable {
constructor := func(parent BinarySearchable, value interface{}) BinarySearchable {
return &RedBlackTree{&BinarySearchTree{value: value, less: tree.less, parent: parent}, Red}
}
inserted := insert(tree, value, constructor).(*RedBlackTree)
inserted.balance()
return inserted
}
func (tree *RedBlackTree) balance() {
// ...omitted for brevity
}
如果有人有更地道的设计,或改进此设计的建议,请发表答案,我会采纳。
关于go - 在 Go 中实现红黑树的惯用方法是什么?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/23507266/