2025-01-14 v. 8.0.2: added "968. Binary Tree Cameras"

Author: fartem

README.md

@@ -671,3 +671,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 871. Minimum Number of Refueling Stops        | [Link](https://leetcode.com/problems/minimum-number-of-refueling-stops/)         | [Link](./lib/hard/871_minimum_number_of_refueling_stops.rb)        | [Link](./test/hard/test_871_minimum_number_of_refueling_stops.rb)        |
 | 895. Maximum Frequency Stack                  | [Link](https://leetcode.com/problems/maximum-frequency-stack/)                   | [Link](./lib/hard/895_maximum_frequency_stack.rb)                  | [Link](./test/hard/test_895_maximum_frequency_stack.rb)                  |
 | 936. Stamping The Sequence                    | [Link](https://leetcode.com/problems/stamping-the-sequence/)                     | [Link](./lib/hard/936_stamping_the_sequence.rb)                    | [Link](./test/hard/test_936_stamping_the_sequence.rb)                    |
+| 968. Binary Tree Cameras                      | [Link](https://leetcode.com/problems/binary-tree-cameras/)                       | [Link](./lib/hard/968_binary_tree_cameras.rb)                      | [Link](./test/hard/test_968_binary_tree_cameras.rb)                      |

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 = '8.0.1'
+  s.version = '8.0.2'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/common/binary_tree.rb

@@ -39,7 +39,4 @@ def ==(other)
   # @param {TreeNode} other
   # @return {Boolean}
   def eql?(other) = self == other
-
-  # @return {Integer}
-  def hash = [@val].hash
 end

lib/hard/968_binary_tree_cameras.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: false
+
+# https://leetcode.com/problems/binary-tree-cameras/
+# @param {TreeNode} root
+# @return {Integer}
+def min_camera_cover(root)
+  @result = 0
+  dfs_for_min_camera_cover(::Set.new([nil]), root, nil)
+
+  @result
+end
+
+private
+
+# @param {Set} cov
+# @param {TreeNode} node
+# @param {TreeNode} par
+# @return {Void}
+def dfs_for_min_camera_cover(cov, node, par)
+  return unless node
+
+  dfs_for_min_camera_cover(cov, node.left, node)
+  dfs_for_min_camera_cover(cov, node.right, node)
+
+  return unless !par && !cov.include?(node) || !cov.include?(node.left) || !cov.include?(node.right)
+
+  @result += 1
+
+  cov << node
+  cov << par
+  cov << node.left
+  cov << node.right
+end

test/hard/test_968_binary_tree_cameras.rb

@@ -0,0 +1,50 @@
+# frozen_string_literal: false
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/hard/968_binary_tree_cameras'
+require 'minitest/autorun'
+
+class BinaryTreeCamerasTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      1,
+      min_camera_cover(
+        ::TreeNode.new(
+          0,
+          ::TreeNode.new(
+            0,
+            ::TreeNode.new(0),
+            ::TreeNode.new(0)
+          ),
+          nil
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      2,
+      min_camera_cover(
+        ::TreeNode.new(
+          0,
+          ::TreeNode.new(
+            0,
+            ::TreeNode.new(
+              0,
+              ::TreeNode.new(
+                0,
+                nil,
+                ::TreeNode.new(0)
+              ),
+              nil
+            ),
+            nil
+          ),
+          nil
+        )
+      )
+    )
+  end
+end