diff --git a/README.md b/README.md
index 51e1d4d9..5f17585d 100644
--- a/README.md
+++ b/README.md
@@ -653,6 +653,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 981. Time Based Key-Value Store                                  | [Link](https://leetcode.com/problems/time-based-key-value-store/)                                  | [Link](./lib/medium/981_time_based_key_value_store.rb)                                  | [Link](./test/medium/test_981_time_based_key_value_store.rb)                                  |
 | 985. Sum of Even Numbers After Queries                           | [Link](https://leetcode.com/problems/sum-of-even-numbers-after-queries/)                           | [Link](./lib/medium/985_sum_of_even_numbers_after_queries.rb)                           | [Link](./test/medium/test_985_sum_of_even_numbers_after_queries.rb)                           |
 | 988. Smallest String Starting From Leaf                          | [Link](https://leetcode.com/problems/smallest-string-starting-from-leaf/)                          | [Link](./lib/medium/988_smallest_string_starting_from_leaf.rb)                          | [Link](./test/medium/test_988_smallest_string_starting_from_leaf.rb)                          |
+| 998. Maximum Binary Tree II                                      | [Link](https://leetcode.com/problems/maximum-binary-tree-ii/)                                      | [Link](./lib/medium/998_maximum_binary_tree_ii.rb)                                      | [Link](./test/medium/test_998_maximum_binary_tree_ii.rb)                                      |
 | 1400. Construct K Palindrome Strings                             | [Link](https://leetcode.com/problems/construct-k-palindrome-strings/)                              | [Link](./lib/medium/1400_construct_k_palindrome_strings.rb)                             | [Link](./test/medium/test_1400_construct_k_palindrome_strings.rb)                             |
 | 2116. Check if a Parentheses String Can Be Valid                 | [Link](https://leetcode.com/problems/check-if-a-parentheses-string-can-be-valid/)                  | [Link](./lib/medium/2116_check_if_a_parentheses_string_can_be_valid.rb)                 | [Link](./test/medium/test_2116_check_if_a_parentheses_string_can_be_valid.rb)                 |
 | 2425. Bitwise XOR of All Pairings                                | [Link](https://leetcode.com/problems/bitwise-xor-of-all-pairings/)                                 | [Link](./lib/medium/2425_bitwise_xor_of_all_pairings.rb)                                | [Link](./test/medium/test_2425_bitwise_xor_of_all_pairings.rb)                                |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index d0894393..befe9e38 100644
--- a/leetcode-ruby.gemspec
+++ b/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 = '8.2.0'
+  s.version = '8.2.1'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/998_maximum_binary_tree_ii.rb b/lib/medium/998_maximum_binary_tree_ii.rb
new file mode 100644
index 00000000..d04d5573
--- /dev/null
+++ b/lib/medium/998_maximum_binary_tree_ii.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+require_relative '../common/binary_tree'
+
+# https://leetcode.com/problems/maximum-binary-tree-ii/
+# @param {TreeNode} root
+# @param {Integer} val
+# @return {TreeNode}
+def insert_into_max_tree(root, val)
+  return unless root
+
+  if root.val < val
+    node = ::TreeNode.new(val)
+    node.left = root
+
+    return node
+  else
+    root.right =
+      if root.right
+        insert_into_max_tree(root.right, val)
+      else
+        ::TreeNode.new(val)
+      end
+  end
+
+  root
+end
diff --git a/test/medium/test_998_maximum_binary_tree_ii.rb b/test/medium/test_998_maximum_binary_tree_ii.rb
new file mode 100644
index 00000000..b107e529
--- /dev/null
+++ b/test/medium/test_998_maximum_binary_tree_ii.rb
@@ -0,0 +1,104 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/common/binary_tree'
+require_relative '../../lib/medium/998_maximum_binary_tree_ii'
+require 'minitest/autorun'
+
+class MaximumBinaryTreeIITest < ::Minitest::Test
+  def test_default_one
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          5,
+          ::TreeNode.new(
+            4,
+            ::TreeNode.new(1),
+            ::TreeNode.new(
+              3,
+              ::TreeNode.new(2),
+              nil
+            )
+          ),
+          nil
+        ),
+        insert_into_max_tree(
+          ::TreeNode.new(
+            4,
+            ::TreeNode.new(1),
+            ::TreeNode.new(
+              3,
+              ::TreeNode.new(2),
+              nil
+            )
+          ),
+          5
+        )
+      )
+    )
+  end
+
+  def test_default_two
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          5,
+          ::TreeNode.new(
+            2,
+            nil,
+            ::TreeNode.new(1)
+          ),
+          ::TreeNode.new(
+            4,
+            nil,
+            ::TreeNode.new(3)
+          )
+        ),
+        insert_into_max_tree(
+          ::TreeNode.new(
+            5,
+            ::TreeNode.new(
+              2,
+              nil,
+              ::TreeNode.new(1)
+            ),
+            ::TreeNode.new(4)
+          ),
+          3
+        )
+      )
+    )
+  end
+
+  def test_default_three
+    assert(
+      ::TreeNode.are_equals(
+        ::TreeNode.new(
+          5,
+          ::TreeNode.new(
+            2,
+            nil,
+            ::TreeNode.new(1)
+          ),
+          ::TreeNode.new(
+            4,
+            ::TreeNode.new(3),
+            nil
+          )
+        ),
+        insert_into_max_tree(
+          ::TreeNode.new(
+            5,
+            ::TreeNode.new(
+              2,
+              nil,
+              ::TreeNode.new(1)
+            ),
+            ::TreeNode.new(3)
+          ),
+          4
+        )
+      )
+    )
+  end
+end