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rbtree.go
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rbtree.go
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package collections
import "math"
type Comparable interface {
int64 | int | float64 | uint | uint64 | string
}
type CompareFn[K Comparable] func(key1, key2 K) int
type Node[K Comparable, V any] struct {
key K
val V
left *Node[K, V]
right *Node[K, V]
size int
color Color
}
func (n *Node[K, V]) Key() K {
return n.key
}
func (n *Node[K, V]) Val() V {
return n.val
}
type RBTree[K Comparable, V any] struct {
root *Node[K, V]
compareFn CompareFn[K]
}
type Color int
const (
Red Color = iota
Black
)
func New[K Comparable, V any]() *RBTree[K, V] {
return &RBTree[K, V]{}
}
func NewWithComparator[K Comparable, V any](compareFn CompareFn[K]) *RBTree[K, V] {
return &RBTree[K, V]{
compareFn: compareFn,
}
}
func (t *RBTree[K, V]) Put(key K, val V) {
t.root = put(t.root, key, val, t.compareFn)
t.root.color = Black
}
func (t *RBTree[K, V]) Get(key K) (V, bool) {
return get(t.root, key, t.compareFn)
}
func (t *RBTree[K, V]) IsEmpty() bool {
return t.root.size == 0
}
func (t *RBTree[K, V]) Min() *Node[K, V] {
if t.IsEmpty() {
return &Node[K, V]{}
}
return min(t.root)
}
func (t *RBTree[K, V]) Max() *Node[K, V] {
if t.IsEmpty() {
return &Node[K, V]{}
}
return max(t.root)
}
func (t *RBTree[K, V]) Size() int {
return size(t.root)
}
func (t *RBTree[K, V]) DeleteMin() {
if !isRed(t.root.left) && !isRed(t.root.right) {
t.root.color = Red
}
t.root = deleteMin(t.root)
if !t.IsEmpty() {
t.root.color = Black
}
}
func (t *RBTree[K, V]) DeleteMax() {
if !isRed(t.root.left) && !isRed(t.root.right) {
t.root.color = Red
}
t.root = deleteMax(t.root)
if !t.IsEmpty() {
t.root.color = Black
}
}
func (t *RBTree[K, V]) Delete(key K) {
if !t.Has(key) {
return
}
if !isRed(t.root.left) && !isRed(t.root.right) {
t.root.color = Red
}
t.root = deleteNode(t.root, key, t.compareFn)
if !t.IsEmpty() {
t.root.color = Black
}
}
func (t *RBTree[K, V]) Height() int {
return int(height(t.root))
}
func (t *RBTree[K, V]) Has(key K) bool {
_, ok := t.Get(key)
return ok
}
func (t *RBTree[K, V]) Keys() []K {
keys := make([]K, 0, size(t.root))
return inOrder(t.root, keys)
}
func (t *RBTree[K, V]) Rank(key K) int {
return rank(t.root, key, t.compareFn)
}
func rank[K Comparable, V any](node *Node[K, V], key K, compareFn CompareFn[K]) int {
if node == nil {
return 0
}
cmp := compare(key, node.key, compareFn)
if cmp < 0 {
return rank(node.left, key, compareFn)
}
if cmp > 0 {
return 1 + size(node.left) + rank(node.right, key, compareFn)
}
return size(node.left)
}
func inOrder[K Comparable, V any](node *Node[K, V], keys []K) []K {
if node == nil {
return keys
}
keys = inOrder(node.left, keys)
keys = append(keys, node.key)
keys = inOrder(node.right, keys)
return keys
}
func isRed[K Comparable, V any](node *Node[K, V]) bool {
if node == nil {
return false
}
return node.color == Red
}
func height[K Comparable, V any](node *Node[K, V]) float64 {
if node == nil {
return -1
}
return 1 + math.Max(height(node.left), height(node.right))
}
func deleteNode[K Comparable, V any](node *Node[K, V], key K, compareFn CompareFn[K]) *Node[K, V] {
if compare(key, node.key, compareFn) < 0 {
if !isRed(node.left) && !isRed(node.left.left) {
node = moveRedLeft(node)
}
node.left = deleteNode(node.left, key, compareFn)
return balance(node)
}
if isRed(node.left) {
node = rotateRight(node)
}
if compare(key, node.key, compareFn) == 0 && node.right == nil {
return nil
}
if !isRed(node.right) && !isRed(node.right.left) {
node = moveRedRight(node)
}
if compare(key, node.key, compareFn) == 0 {
x := min(node.right)
node.key = x.key
node.val = x.val
node.right = deleteMin(node.right)
} else {
node.right = deleteNode(node.right, key, compareFn)
}
return balance(node)
}
func deleteMax[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
if isRed(node.left) {
node = rotateRight(node)
}
if node.right == nil {
return nil
}
if !isRed(node.right) && !isRed(node.right.left) {
node = moveRedRight(node)
}
node.right = deleteMax(node.right)
return balance(node)
}
func deleteMin[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
if node.left == nil {
return nil
}
if !isRed(node.left) && !isRed(node.left.left) {
node = moveRedLeft(node)
}
node.left = deleteMin(node.left)
return balance(node)
}
func max[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
if node.right == nil {
return node
}
return max(node.right)
}
func min[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
if node.left == nil {
return node
}
return min(node.left)
}
func get[K Comparable, V any](node *Node[K, V], key K, compareFn CompareFn[K]) (V, bool) {
if node == nil {
return (&Node[K, V]{}).val, false // hack to workaround generics zero value with correct type
}
cmp := compare(key, node.key, compareFn)
if cmp < 0 {
return get(node.left, key, compareFn)
}
if cmp > 0 {
return get(node.right, key, compareFn)
}
return node.val, true
}
func put[K Comparable, V any](node *Node[K, V], key K, val V, compareFn CompareFn[K]) *Node[K, V] {
if node == nil {
return &Node[K, V]{
key: key,
val: val,
size: 1,
color: Red,
}
}
cmp := compare(key, node.key, compareFn)
if cmp < 0 {
node.left = put(node.left, key, val, compareFn)
} else if cmp > 0 {
node.right = put(node.right, key, val, compareFn)
} else {
node.val = val
}
return balance(node)
}
func size[K Comparable, V any](node *Node[K, V]) int {
if node == nil {
return 0
}
return int(node.size)
}
func compare[K Comparable](key1, key2 K, compareFn CompareFn[K]) int {
if compareFn != nil {
return compareFn(key1, key2)
}
if key1 < key2 {
return -1
}
if key1 > key2 {
return 1
}
return 0
}
func rotateLeft[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
x := node.right
node.right = x.left
x.left = node
x.color = node.color
node.color = Red
x.size = node.size
node.size = size(node.left) + size(node.right) + 1
return x
}
func rotateRight[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
x := node.left
node.left = x.right
x.right = node
x.color = node.color
node.color = Red
x.size = node.size
node.size = size(node.left) + size(node.right) + 1
return x
}
func flipColors[K Comparable, V any](node *Node[K, V]) {
// bitwise xor to flip colors (0 and 1)
node.color ^= node.color
node.left.color ^= node.left.color
node.right.color ^= node.right.color
}
func balance[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
if isRed(node.right) && !isRed(node.left) {
node = rotateLeft(node)
}
if isRed(node.left) && isRed(node.left.left) {
node = rotateRight(node)
}
if isRed(node.left) && isRed(node.right) {
flipColors(node)
}
node.size = size(node.left) + size(node.right) + 1
return node
}
func moveRedRight[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
flipColors(node)
if isRed(node.left.left) {
node = rotateRight(node)
flipColors(node)
}
return node
}
func moveRedLeft[K Comparable, V any](node *Node[K, V]) *Node[K, V] {
flipColors(node)
if isRed(node.right.left) {
node.right = rotateRight(node.right)
node = rotateLeft(node)
flipColors(node)
}
return node
}