2025-01-06 v. 7.7.1: added "863. All Nodes Distance K in Binary Tree"

Author: fartem

README.md

@@ -629,6 +629,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 852. Peak Index in a Mountain Array                             | [Link](https://leetcode.com/problems/peak-index-in-a-mountain-array/)                             | [Link](./lib/medium/852_peak_index_in_a_mountain_array.rb)                             | [Link](./test/medium/test_852_peak_index_in_a_mountain_array.rb)                             |
 | 856. Score of Parentheses                                       | [Link](https://leetcode.com/problems/score-of-parentheses/)                                       | [Link](./lib/medium/856_score_of_parentheses.rb)                                       | [Link](./test/medium/test_856_score_of_parentheses.rb)                                       |
 | 858. Mirror Reflection                                          | [Link](https://leetcode.com/problems/mirror-reflection/)                                          | [Link](./lib/medium/858_mirror_reflection.rb)                                          | [Link](./test/medium/test_858_mirror_reflection.rb)                                          |
+| 863. All Nodes Distance K in Binary Tree                        | [Link](https://leetcode.com/problems/all-nodes-distance-k-in-binary-tree/)                        | [Link](./lib/medium/863_all_nodes_distance_k_in_binary_tree.rb)                        | [Link](./test/medium/test_863_all_nodes_distance_k_in_binary_tree.rb)                        |
 
 ### Hard
 

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '7.7.0'
+  s.version = '7.7.1'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/common/binary_tree.rb

@@ -35,4 +35,11 @@ def ==(other)
 
     val == other.val
   end
+
+  # @param {TreeNode} other
+  # @return {Boolean}
+  def eql?(other) = self == other
+
+  # @return {Integer}
+  def hash = [@val].hash
 end

lib/medium/863_all_nodes_distance_k_in_binary_tree.rb

@@ -0,0 +1,41 @@
+# frozen_string_literal: true
+
+require 'set'
+
+# https://leetcode.com/problems/all-nodes-distance-k-in-binary-tree/
+# @param {TreeNode} root
+# @param {TreeNode} target
+# @param {Integer} k
+# @return {Integer[]}
+def distance_k(root, target, k)
+  @parent = {}
+  patch!(root, nil)
+
+  seen = [target].to_set
+  curr = [target].to_set
+
+  loop do
+    return curr.map(&:val) if k.zero?
+
+    curr = curr.flat_map { |node| [@parent[node], node.left, node.right] }
+               .tap(&:compact!)
+               .to_set
+               .difference(seen)
+
+    seen.merge(curr)
+
+    k -= 1
+  end
+end
+
+# @param {TreeNode} node
+# @param {TreeNode} parent
+# @return {Void}
+def patch!(node, parent)
+  return unless node
+
+  @parent[node] = parent
+
+  patch!(node.left, node)
+  patch!(node.right, node)
+end

test/medium/test_863_all_nodes_distance_k_in_binary_tree.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/863_all_nodes_distance_k_in_binary_tree'
+require 'minitest/autorun'
+
+class AllNodesDistanceKInBinaryTreeTest < ::Minitest::Test
+  def test_default_one
+    target = ::TreeNode.new(
+      5,
+      ::TreeNode.new(6),
+      ::TreeNode.new(
+        2,
+        ::TreeNode.new(7),
+        ::TreeNode.new(4)
+      )
+    )
+
+    assert_equal(
+      [1, 7, 4],
+      distance_k(
+        ::TreeNode.new(
+          3,
+          target,
+          ::TreeNode.new(
+            1,
+            ::TreeNode.new(0),
+            ::TreeNode.new(8)
+          )
+        ),
+        target,
+        2
+      )
+    )
+  end
+
+  def test_default_two
+    target = ::TreeNode.new(1)
+
+    assert_equal(
+      [],
+      distance_k(
+        target,
+        target,
+        3
+      )
+    )
+  end
+end