diff --git a/README.md b/README.md
index 51407117..85312e48 100644
--- a/README.md
+++ b/README.md
@@ -733,6 +733,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 2091. Removing Minimum and Maximum From Array                                       | [Link](https://leetcode.com/problems/removing-minimum-and-maximum-from-array/)                                       | [Link](./lib/medium/2091_removing_minimum_and_maximum_from_array.rb)                                       | [Link](./test/medium/test_2091_removing_minimum_and_maximum_from_array.rb)                                       |
 | 2095. Delete the Middle Node of a Linked List                                       | [Link](https://leetcode.com/problems/delete-the-middle-node-of-a-linked-list/)                                       | [Link](./lib/medium/2095_delete_the_middle_node_of_a_linked_list.rb)                                       | [Link](./test/medium/test_2095_delete_the_middle_node_of_a_linked_list.rb)                                       |
 | 2096. Step-By-Step Directions From a Binary Tree Node to Another                    | [Link](https://leetcode.com/problems/step-by-step-directions-from-a-binary-tree-node-to-another/)                    | [Link](./lib/medium/2096_step_by_step_directions_from_a_binary_tree_node_to_another.rb)                    | [Link](./test/medium/test_2096_step_by_step_directions_from_a_binary_tree_node_to_another.rb)                    |
+| 2109. Adding Spaces to a String                                                     | [Link](https://leetcode.com/problems/adding-spaces-to-a-string/)                                                     | [Link](./lib/medium/2109_adding_spaces_to_a_string.rb)                                                     | [Link](./test/medium/test_2109_adding_spaces_to_a_string.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)                                                   |
 | 2429. Minimize XOR                                                                  | [Link](https://leetcode.com/problems/minimize-xor/)                                                                  | [Link](./lib/medium/2429_minimize_xor.rb)                                                                  | [Link](./test/medium/test_2429_minimize_xor.rb)                                                                  |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index 06b681bf..165932fc 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 = '8.9.9'
+  s.version = '9.0.0'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/2109_adding_spaces_to_a_string.rb b/lib/medium/2109_adding_spaces_to_a_string.rb
new file mode 100644
index 00000000..b27c7e62
--- /dev/null
+++ b/lib/medium/2109_adding_spaces_to_a_string.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/adding-spaces-to-a-string/
+# @param {String} s
+# @param {Integer[]} spaces
+# @return {String}
+def add_spaces(s, spaces)
+  start = 0
+  result = []
+
+  spaces.each do |space|
+    result << s[start...space]
+    result << ' '
+    start = space
+  end
+
+  result << s[start..]
+
+  result.join
+end
diff --git a/test/medium/test_2109_adding_spaces_to_a_string.rb b/test/medium/test_2109_adding_spaces_to_a_string.rb
new file mode 100644
index 00000000..2a240416
--- /dev/null
+++ b/test/medium/test_2109_adding_spaces_to_a_string.rb
@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/2109_adding_spaces_to_a_string'
+require 'minitest/autorun'
+
+class AddingSpacesToAStringTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      'Leetcode Helps Me Learn',
+      add_spaces(
+        'LeetcodeHelpsMeLearn',
+        [8, 13, 15]
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      'i code in py thon',
+      add_spaces(
+        'icodeinpython',
+        [1, 5, 7, 9]
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      ' s p a c i n g',
+      add_spaces(
+        'spacing',
+        [0, 1, 2, 3, 4, 5, 6]
+      )
+    )
+  end
+end