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|
package search
import "fmt"
type linkColor bool
const (
red linkColor = true
black linkColor = false
)
type rbNode struct {
key int
val int
left *rbNode
right *rbNode
color linkColor
}
func (n *rbNode) String() string {
recurse := func(n *rbNode) string {
if n == nil {
return ""
}
return n.String()
}
return fmt.Sprintf("rbNode{%d:%d,%v,%s,%s}",
n.key,
n.val,
n.color,
recurse(n.left),
recurse(n.right),
)
}
type RedBlackBST struct {
root *rbNode
}
func NewRedBlackBST() *RedBlackBST {
return &RedBlackBST{}
}
func (t *RedBlackBST) String() string {
if t.Empty() {
return "RedBlackBST{}"
}
return fmt.Sprintf("RedBlackBST{%s}", t.root)
}
func (t *RedBlackBST) Empty() bool {
return t.root == nil
}
func (t *RedBlackBST) Put(key, val int) {
if t.Empty() {
t.root = &rbNode{key, val, nil, nil, black}
return
}
parent, ptr, _, err := t.search(nil, &t.root, key)
switch err {
case nil:
// key already in the tree
return
case NotFound:
*ptr = &rbNode{key, val, nil, nil, red}
return
default:
panic(err)
}
t.balance(parent)
}
func (t *RedBlackBST) balance(n *rbNode) {
switch {
case n == nil, n.right == nil:
return
case n.right.color == black:
return
case n.left.color == black:
// Left is black and right is red
case n.left.color == red:
// Left and right are red
}
}
func (t *RedBlackBST) Get(key int) (int, error) {
_, _, n, err := t.search(nil, &t.root, key)
if err != nil {
return 0, err
}
return n.val, nil
}
func (t *RedBlackBST) Del(key int) (int, error) {
_, ptr, n, err := t.search(nil, &t.root, key)
if err != nil {
return 0, err
}
// Case 1: n is leaf rbNode
// Case 2: n has one child
// Case 3: n has two childs
switch {
case n.left == nil:
if n.right == nil {
// I am a leaf rbNode
*ptr = nil
return n.val, nil
}
// I have a right child
*ptr = n.right
return n.val, nil
case n.right == nil:
// I have a left child
*ptr = n.left
return n.val, nil
default:
// I have two children!
o, err := t.deleteMin(&n.right)
if err != nil {
return 0, err
}
o.left = n.left
o.right = n.right
*ptr = o
return n.val, nil
}
}
func (t *RedBlackBST) search(parent *rbNode, ptr **rbNode, key int) (*rbNode, **rbNode, *rbNode, error) {
n := *ptr
if n == nil {
return parent, ptr, nil, NotFound
}
switch {
case key < n.key:
return t.search(n, &n.left, key)
case n.key < key:
return t.search(n, &n.right, key)
default:
return parent, ptr, n, nil
}
}
func (t *RedBlackBST) deleteMin(ptr **rbNode) (*rbNode, error) {
ptr, n, err := t.min(ptr)
if err != nil {
return nil, err
}
*ptr = n.right
n.right = nil
return n, nil
}
func (t *RedBlackBST) min(ptr **rbNode) (**rbNode, *rbNode, error) {
n := *ptr
if n == nil {
return nil, nil, NotFound
}
for {
if n.left == nil {
return ptr, n, nil
}
ptr = &n.left
n = *ptr
}
}
func (t *RedBlackBST) rotateLeft(ptr **rbNode) {
x := *ptr
y := x.right
x.right = y.left
x.left = y
*ptr = y
x.color = red
y.color = black
}
func (t *RedBlackBST) rotateRight(ptr **rbNode) {
y := *ptr
x := y.right
y.left = x.right
x.right = y
*ptr = x
x.color = black
y.color = red
}
func (t *RedBlackBST) flipColors(n *rbNode) {
n.left.color = black
n.right.color = black
n.color = red
}
|
