mirror of
https://github.com/emirpasic/gods
synced 2024-11-06 15:20:25 +00:00
355 lines
8.0 KiB
Go
355 lines
8.0 KiB
Go
/*
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Copyright (c) Emir Pasic, All rights reserved.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 3.0 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library. See the file LICENSE included
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with this distribution for more information.
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*/
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// Implementation of Red-black tree.
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// Used by TreeSet and TreeMap.
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// References: http://en.wikipedia.org/wiki/Red%E2%80%93black_tree
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package redblacktree
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import (
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"github.com/emirpasic/gods/utils"
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"log"
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)
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type Color bool
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const (
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BLACK, RED Color = true, false
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)
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type Tree struct {
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root *Node
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comparator utils.Comparator
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}
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type Node struct {
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key interface{}
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value interface{}
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color Color
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left *Node
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right *Node
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parent *Node
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}
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// Instantiates a red-black tree with the custom comparator.
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func NewWith(comparator utils.Comparator) *Tree {
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return &Tree{comparator: comparator}
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}
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// Instantiates a red-black tree with the IntComparator, i.e. keys are of type int.
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func NewWithIntComparator() *Tree {
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return &Tree{comparator: utils.IntComparator}
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}
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// Instantiates a red-black tree with the StringComparator, i.e. keys are of type string.
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func NewWithStringComparator() *Tree {
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return &Tree{comparator: utils.StringComparator}
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}
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// Inserts node into the tree.
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// Key should adhere to the comparator's type assertion, otherwise method panics.
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func (tree *Tree) Put(key interface{}, value interface{}) {
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insertedNode := &Node{key: key, value: value, color: RED}
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if tree.root == nil {
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tree.root = insertedNode
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} else {
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node := tree.root
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loop := true
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for loop {
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compare := tree.comparator(key, node.key)
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switch {
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case compare == 0:
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node.value = value
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return
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case compare < 0:
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if node.left == nil {
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node.left = insertedNode
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loop = false
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} else {
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node = node.left
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}
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case compare > 0:
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if node.right == nil {
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node.right = insertedNode
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break
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} else {
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node = node.right
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}
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}
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}
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insertedNode.parent = node
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}
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tree.insertCase1(insertedNode)
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}
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// Searches the node in the tree by key and returns its value or nil if key is not found in tree.
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// Second return parameter is true if key was found, otherwise false.
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// Key should adhere to the comparator's type assertion, otherwise method panics.
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func (tree *Tree) Get(key interface{}) (interface{}, bool) {
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node := tree.lookup(key)
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if node != nil {
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return node.value, true
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}
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return nil, false
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}
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// Remove the node from the tree by key.
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// Key should adhere to the comparator's type assertion, otherwise method panics.
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func (tree *Tree) Remove(key interface{}) {
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var child *Node
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node := tree.lookup(key)
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if node == nil {
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return
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}
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if node.left != nil && node.right != nil {
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pred := node.left.maximumNode()
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node.key = pred.key
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node.value = pred.value
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node = pred
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}
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if node.right == nil {
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child = node.left
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} else {
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child = node.right
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}
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if node.color == BLACK {
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node.color = child.color
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tree.deleteCase1(node)
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}
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tree.replaceNode(node, child)
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if node.parent == nil && child != nil {
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child.color = BLACK
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}
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}
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// Returns true if tree does not contain any nodes
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func (tree *Tree) IsEmpty() bool {
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return tree.root == nil
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}
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func (tree *Tree) lookup(key interface{}) *Node {
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node := tree.root
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for node != nil {
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compare := tree.comparator(key, node.key)
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switch {
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case compare == 0:
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return node
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case compare < 0:
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node = node.left
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case compare > 0:
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node = node.right
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}
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}
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return nil
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}
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func (node *Node) grandparent() *Node {
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if node != nil && node.parent != nil {
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return node.parent.parent
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}
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return nil
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}
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func (node *Node) uncle() *Node {
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grandparent := node.grandparent()
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switch {
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case grandparent == nil:
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return nil
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case node.parent == grandparent.left:
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return grandparent.right
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default:
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return grandparent.left
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}
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}
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func (tree *Tree) rotateLeft(node *Node) {
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right := node.right
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tree.replaceNode(node, right)
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node.right = right.left
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if right.left != nil {
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right.left.parent = node
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}
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right.left = node
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node.parent = right
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}
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func (tree *Tree) rotateRight(node *Node) {
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left := node.left
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tree.replaceNode(node, left)
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node.left = left.right
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if left.right != nil {
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left.right.parent = node
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}
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left.right = node
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node.parent = left
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}
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func (tree *Tree) replaceNode(old *Node, new *Node) {
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if old.parent == nil {
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tree.root = new
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} else {
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if old == old.parent.left {
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old.parent.left = new
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} else {
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old.parent.right = new
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}
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}
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if new != nil {
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new.parent = old.parent
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}
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}
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func (tree *Tree) insertCase1(node *Node) {
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if node.parent == nil {
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node.color = BLACK
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} else {
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tree.insertCase2(node)
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}
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}
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func (tree *Tree) insertCase2(node *Node) {
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if node.parent.color == BLACK {
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return /* Tree is still valid */
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}
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tree.insertCase3(node)
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}
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func (tree *Tree) insertCase3(node *Node) {
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log.Printf("%#v\n", node)
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if node.uncle().color == RED {
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node.parent.color = BLACK
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node.uncle().color = BLACK
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node.grandparent().color = RED
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tree.insertCase1(node.grandparent())
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} else {
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tree.insertCase4(node)
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}
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}
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func (tree *Tree) insertCase4(node *Node) {
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if node == node.parent.right && node.parent == node.grandparent().left {
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tree.rotateLeft(node.parent)
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node = node.left
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} else if node == node.parent.left && node.parent == node.grandparent().right {
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tree.rotateRight(node.parent)
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node = node.right
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}
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tree.insertCase5(node)
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}
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func (tree *Tree) insertCase5(node *Node) {
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node.parent.color = BLACK
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node.grandparent().color = RED
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if node == node.parent.left && node.parent == node.grandparent().left {
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tree.rotateRight(node.grandparent())
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} else {
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tree.rotateLeft(node.grandparent())
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}
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}
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func (node *Node) maximumNode() *Node {
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for node.right != nil {
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node = node.right
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}
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return node
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}
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func (node *Node) sibling() *Node {
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if node == node.parent.left {
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return node.parent.right
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} else {
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return node.parent.left
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}
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}
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func (tree *Tree) deleteCase1(node *Node) {
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if node.parent == nil {
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return
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} else {
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tree.deleteCase2(node)
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}
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}
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func (tree *Tree) deleteCase2(node *Node) {
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if node.sibling().color == RED {
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node.parent.color = RED
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node.sibling().color = BLACK
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if node == node.parent.left {
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tree.rotateLeft(node.parent)
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} else {
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tree.rotateRight(node.parent)
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}
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}
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tree.deleteCase3(node)
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}
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func (tree *Tree) deleteCase3(node *Node) {
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if node.parent.color == BLACK &&
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node.sibling().color == BLACK &&
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node.sibling().left.color == BLACK &&
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node.sibling().right.color == BLACK {
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node.sibling().color = RED
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tree.deleteCase1(node.parent)
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} else {
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tree.deleteCase4(node)
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}
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}
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func (tree *Tree) deleteCase4(node *Node) {
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if node.parent.color == RED &&
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node.sibling().color == BLACK &&
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node.sibling().left.color == BLACK &&
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node.sibling().right.color == BLACK {
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node.sibling().color = RED
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node.parent.color = BLACK
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} else {
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tree.deleteCase5(node)
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}
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}
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func (tree *Tree) deleteCase5(node *Node) {
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if node == node.parent.left &&
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node.sibling().color == BLACK &&
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node.sibling().left.color == RED &&
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node.sibling().right.color == BLACK {
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node.sibling().color = RED
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node.sibling().left.color = BLACK
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tree.rotateRight(node.sibling())
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} else if node == node.parent.right &&
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node.sibling().color == BLACK &&
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node.sibling().right.color == RED &&
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node.sibling().left.color == BLACK {
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node.sibling().color = RED
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node.sibling().right.color = BLACK
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tree.rotateLeft(node.sibling())
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}
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tree.deleteCase6(node)
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}
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func (tree *Tree) deleteCase6(node *Node) {
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node.sibling().color = node.parent.color
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node.parent.color = BLACK
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if node == node.parent.left {
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node.sibling().right.color = BLACK
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tree.rotateLeft(node.parent)
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} else {
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node.sibling().left.color = BLACK
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tree.rotateRight(node.parent)
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}
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}
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