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Commit e6ae910

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Merge pull request #334 from itsmegrave/main
✨ Add ruby BST
2 parents 9b7e6d2 + 2227ce5 commit e6ae910

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2 files changed

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‎README.md‎

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@@ -1776,8 +1776,8 @@ In order to achieve greater coverage and encourage more people to contribute to
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</a>
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</td>
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<td> <!-- Ruby -->
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<a href="./CONTRIBUTING.md">
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<img align="center" height="25" src="./logos/github.svg" />
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<a href="./src/ruby/binary_search_tree.rb">
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<img align="center" height="25" src="./logos/ruby.svg" />
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</a>
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</td>
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<td> <!-- JavaScript -->

‎src/ruby/binary_search_tree.rb‎

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# frozen_string_literal: true
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class BinarySearchTree
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class Node
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attr_accessor :left, :right, :value
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def initialize(value)
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@left = nil
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@right = nil
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@value = value
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end
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end
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def initialize
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@root = nil
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end
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attr_reader :root
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def insert(value)
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new_node = Node.new(value)
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if @root.nil?
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@root = new_node
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return self
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end
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current_node = @root
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loop do
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if value < current_node.value
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if current_node.left.nil?
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current_node.left = new_node
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return self
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end
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current_node = current_node.left
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else
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if current_node.right.nil?
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current_node.right = new_node
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return self
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end
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current_node = current_node.right
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end
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end
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self
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end
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def lookup(value)
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return nil if @root.nil?
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current_node = @root
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until current_node.nil?
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if value < current_node.value
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current_node = current_node.left
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elsif value > current_node.value
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current_node = current_node.right
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else
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return current_node
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end
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end
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nil
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end
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def remove(value)
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return false if @root.nil?
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current_node = @root
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parent_node = nil
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while current_node
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if value < current_node.value
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parent_node = current_node
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current_node = current_node.left
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elsif value > current_node.value
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parent_node = current_node
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current_node = current_node.right
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elsif current_node.value == value
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# We have a match, get to work!
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if current_node.right.nil?
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update_parent_link(parent_node, current_node, current_node.left)
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elsif current_node.right.left.nil?
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current_node.right.left = current_node.left
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update_parent_link(parent_node, current_node, current_node.right)
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else
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leftmost, leftmost_parent = find_leftmost(current_node.right)
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leftmost_parent.left = leftmost.right
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leftmost.left = current_node.left
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leftmost.right = current_node.right
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update_parent_link(parent_node, current_node, leftmost)
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end
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return true
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end
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end
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false
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end
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def traverse(node = @root)
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return nil if node.nil?
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tree = { value: node.value }
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tree[:left] = traverse(node.left)
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tree[:right] = traverse(node.right)
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tree
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end
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private
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def update_parent_link(parent_node, current_node, new_node)
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if parent_node.nil?
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@root = new_node
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elsif current_node.value < parent_node.value
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parent_node.left = new_node
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else
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parent_node.right = new_node
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end
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end
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def find_leftmost(node)
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leftmost = node.left
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leftmost_parent = node
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while leftmost.left
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leftmost_parent = leftmost
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leftmost = leftmost.left
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end
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[leftmost, leftmost_parent]
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end
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end
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RSpec.describe BinarySearchTree do
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let(:bst) { BinarySearchTree.new }
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before(:each) do
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# Construct the following tree:
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#
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# 9
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# 4 20
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# 1 6 15 170
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#
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bst.insert(9)
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bst.insert(4)
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bst.insert(6)
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bst.insert(20)
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bst.insert(170)
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bst.insert(15)
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bst.insert(1)
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end
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describe "#insert" do
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it "adds a value to the tree" do
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expect(bst.traverse).to eq({ value: 9,
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left: { value: 4,
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left: { value: 1, left: nil, right: nil },
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right: { value: 6, left: nil, right: nil } },
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right: { value: 20, left: { value: 15, left: nil, right: nil },
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right: { value: 170, left: nil, right: nil } } })
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end
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end
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describe "#lookup" do
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it "finds a value in the tree" do
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node = bst.lookup(15)
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expect(node.value).to eq(15)
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end
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it "returns nil for a value not in the tree" do
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node = bst.lookup(100)
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expect(node).to be_nil
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end
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end
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describe "#remove" do
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it "removes a leaf node" do
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expect(bst.remove(1)).to be true
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expect(bst.traverse).to eq({ value: 9,
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left: { value: 4, left: nil,
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right: { value: 6, left: nil, right: nil } },
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right: { value: 20, left: { value: 15, left: nil, right: nil },
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right: { value: 170, left: nil, right: nil } } })
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end
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it "removes a node with one child" do
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expect(bst.remove(20)).to be true
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expect(bst.traverse).to eq({ value: 9,
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left: { value: 4, left: { value: 1, left: nil, right: nil },
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right: { value: 6, left: nil, right: nil } },
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right: { value: 170, left: { value: 15, left: nil, right: nil },
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right: nil } })
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end
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it "removes a node with two children" do
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expect(bst.remove(4)).to be true
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expect(bst.traverse).to eq({ value: 9,
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left: { value: 6, left: { value: 1, left: nil, right: nil },
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right: nil },
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right: { value: 20, left: { value: 15, left: nil, right: nil },
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right: { value: 170, left: nil, right: nil } } })
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end
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it "returns false for a value not in the tree" do
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expect(bst.remove(100)).to be false
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end
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end
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end

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