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package search
import (
"fmt"
"codeberg.org/snonux/algorithms/ds"
)
type node[K, V ds.Number] struct {
key K
val V
left *node[K,V]
right *node[K,V]
}
func (n *node[K,V]) String() string {
recurse := func(n *node[K,V]) string {
if n == nil {
return ""
}
return n.String()
}
return fmt.Sprintf("node[K,V]{%v:%v,%s,%s}",
n.key,
n.val,
recurse(n.left),
recurse(n.right))
}
type BST[K,V ds.Number] struct {
root *node[K,V]
size int
}
func NewBST[K,V ds.Number]() *BST[K,V] {
return &BST[K,V]{}
}
func (t *BST[K,V]) String() string {
if t.Empty() {
return "BST[K,V]{}"
}
return fmt.Sprintf("BST[K,V]{%s}", t.root)
}
func (t *BST[K,V]) Empty() bool {
return t.root == nil
}
func (t *BST[K,V]) Size() int {
return t.size
}
func (t *BST[K,V]) Put(key K, val V) {
if t.Empty() {
t.root = &node[K,V]{key, val, nil, nil}
t.size++
return
}
ptr, _, err := t.search(&t.root, key)
switch err {
case nil:
// key already in the tree
return
case NotFound:
*ptr = &node[K,V]{key, val, nil, nil}
t.size++
return
default:
panic(err)
}
}
func (t *BST[K,V]) Get(key K) (V, error) {
_, n, err := t.search(&t.root, key)
if err != nil {
return 0, err
}
return n.val, nil
}
func (t *BST[K,V]) Del(key K) (V, error) {
ptr, n, err := t.search(&t.root, key)
if err != nil {
return 0, err
}
t.size--
// Case 1: n is leaf node
// 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 node
*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 *BST[K,V]) search(ptr **node[K,V], key K) (**node[K,V], *node[K,V], error) {
n := *ptr
if n == nil {
return ptr, nil, NotFound
}
switch {
case key < n.key:
return t.search(&n.left, key)
case n.key < key:
return t.search(&n.right, key)
default:
return ptr, n, nil
}
}
func (t *BST[K,V]) deleteMin(ptr **node[K,V]) (*node[K,V], error) {
ptr, n, err := t.min(ptr)
if err != nil {
return nil, err
}
*ptr = n.right
n.right = nil
return n, nil
}
func (t *BST[K,V]) min(ptr **node[K,V]) (**node[K,V], *node[K,V], error) {
n := *ptr
if n == nil {
return nil, nil, NotFound
}
for {
if n.left == nil {
return ptr, n, nil
}
ptr = &n.left
n = *ptr
}
}
|
