diff --git a/README.md b/README.md
index e1d3a7fe..86ac4246 100644
--- a/README.md
+++ b/README.md
@@ -559,3 +559,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 371. Sum of Two Integers                                        | [Link](https://leetcode.com/problems/sum-of-two-integers/)                                        | [Link](./lib/medium/371_sum_of_two_integers.rb)                                        | [Link](./test/medium/test_371_sum_of_two_integers.rb)                                        |
 | 377. Combination Sum IV                                         | [Link](https://leetcode.com/problems/combination-sum-iv/)                                         | [Link](./lib/medium/377_combination_sum_iv.rb)                                         | [Link](./test/medium/test_377_combination_sum_iv.rb)                                         |
 | 378. Kth Smallest Element in a Sorted Matrix                    | [Link](https://leetcode.com/problems/kth-smallest-element-in-a-sorted-matrix/)                    | [Link](./lib/medium/378_kth_smallest_element_in_a_sorted_matrix.rb)                    | [Link](./test/medium/test_378_kth_smallest_element_in_a_sorted_matrix.rb)                    |
+| 380. Insert Delete GetRandom O(1)                               | [Link](https://leetcode.com/problems/insert-delete-getrandom-o1/)                                 | [Link](./lib/medium/380_insert_delete_getrandom_o1.rb)                                 | [Link](./test/medium/test_380_insert_delete_getrandom_o1.rb)                                 |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index d6eb05ea..bf51dc15 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 = '6.9.3'
+  s.version = '6.9.4'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/380_insert_delete_getrandom_o1.rb b/lib/medium/380_insert_delete_getrandom_o1.rb
new file mode 100644
index 00000000..4b5adb55
--- /dev/null
+++ b/lib/medium/380_insert_delete_getrandom_o1.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/insert-delete-getrandom-o1/
+class RandomizedSet
+  # Init
+  def initialize
+    @table = {}
+    @values = []
+  end
+
+  # @param {Integer} val
+  # @return {Boolean}
+  def insert(val)
+    return false if @table[val]
+
+    @table[val] = @values.size
+    @values << val
+
+    true
+  end
+
+  # @param {Integer} val
+  # @return {Boolean}
+  def remove(val)
+    return false unless @table[val]
+
+    last_val = @values.pop
+    unless val == last_val
+      @table[last_val] = @table[val]
+      @values[@table[val]] = last_val
+    end
+
+    @table.delete(val)
+
+    true
+  end
+
+  # @rerturn {Integer}
+  def get_random = @values[rand(@values.size)]
+end
diff --git a/test/medium/test_380_insert_delete_getrandom_o1.rb b/test/medium/test_380_insert_delete_getrandom_o1.rb
new file mode 100644
index 00000000..b646e7a7
--- /dev/null
+++ b/test/medium/test_380_insert_delete_getrandom_o1.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/380_insert_delete_getrandom_o1'
+require 'minitest/autorun'
+
+class InsertDeleteGetRandomO1Test < ::Minitest::Test
+  def test_default_one
+    randomized_set = ::RandomizedSet.new
+    assert(randomized_set.insert(1))
+    assert(!randomized_set.remove(2))
+    assert(randomized_set.insert(2))
+    assert(randomized_set.get_random == 1 || randomized_set.get_random == 2)
+    assert(randomized_set.remove(1))
+    assert(!randomized_set.insert(2))
+    assert_equal(2, randomized_set.get_random)
+  end
+end