diff --git a/README.md b/README.md
index 5c0d42a7..cd09e8a0 100644
--- a/README.md
+++ b/README.md
@@ -599,3 +599,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 621. Task Scheduler                                             | [Link](https://leetcode.com/problems/task-scheduler/)                                             | [Link](./lib/medium/621_task_scheduler.rb)                                             | [Link](./test/medium/test_621_task_scheduler.rb)                                             |
 | 622. Design Circular Queue                                      | [Link](https://leetcode.com/problems/design-circular-queue/)                                      | [Link](./lib/medium/622_design_circular_queue.rb)                                      | [Link](./test/medium/test_622_design_circular_queue.rb)                                      |
 | 623. Add One Row to Tree                                        | [Link](https://leetcode.com/problems/add-one-row-to-tree/)                                        | [Link](./lib/medium/623_add_one_row_to_tree.rb)                                        | [Link](./test/medium/test_623_add_one_row_to_tree.rb)                                        |
+| 641. Design Circular Deque                                      | [Link](https://leetcode.com/problems/design-circular-deque/)                                      | [Link](./lib/medium/641_design_circular_deque.rb)                                      | [Link](./test/medium/test_641_design_circular_deque.rb)                                      |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index 9dbcc97c..ea9344e0 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 = '7.3.4'
+  s.version = '7.3.5'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/641_design_circular_deque.rb b/lib/medium/641_design_circular_deque.rb
new file mode 100644
index 00000000..94e4fdc0
--- /dev/null
+++ b/lib/medium/641_design_circular_deque.rb
@@ -0,0 +1,95 @@
+# frozen_string_literal: true
+
+require_relative '../common/linked_list'
+
+# https://leetcode.com/problems/design-circular-deque/description/
+class MyCircularDeque
+  # @param {Integer} k
+  def initialize(k)
+    @size = k
+    @actual_size = 0
+    @head = ::ListNode.new(0)
+    @tail = nil
+  end
+
+  # @param {Integer} value
+  # @return {Boolean}
+  def insert_front(value)
+    return false if is_full
+
+    new_head = ::ListNode.new(value)
+    if @tail
+      new_head.next = @head.next
+      @head.next = new_head
+    else
+      @tail = new_head
+      @head.next = @tail
+      @tail.next = @head
+    end
+
+    @actual_size += 1
+
+    true
+  end
+
+  # @param {Integer} value
+  # @return {Boolean}
+  def insert_last(value)
+    return false if is_full
+
+    new_tail = ::ListNode.new(value)
+    if @tail
+      @tail.next = new_tail
+    else
+      @head.next = new_tail
+    end
+
+    @tail = new_tail
+    @actual_size += 1
+
+    true
+  end
+
+  # @param {Boolean}
+  def delete_front
+    return false if @actual_size.zero?
+
+    @head.next = @head.next.next
+    @tail = nil if @actual_size == 1
+
+    @actual_size -= 1
+
+    true
+  end
+
+  # @param {Boolean}
+  def delete_last
+    return false if @actual_size.zero?
+
+    if @actual_size == 1
+      @head.next = nil
+      @tail = nil
+    else
+      new_tail = @head.next
+      new_tail = new_tail.next until new_tail.next == @tail
+      new_tail.next = @head
+      @tail = new_tail
+    end
+
+    @actual_size -= 1
+
+    true
+  end
+
+  # @return {Integer}
+  def get_front = @actual_size.zero? ? -1 : @head.next.val
+
+  # @return {Integer}
+  def get_rear = @actual_size.zero? ? -1 : @tail.val
+
+  # @return {Boolean}
+  def is_empty = @actual_size.zero?
+
+  # @return {Boolean}
+  def is_full = @actual_size == @size
+end
diff --git a/test/medium/test_641_design_circular_deque.rb b/test/medium/test_641_design_circular_deque.rb
new file mode 100644
index 00000000..c4a41927
--- /dev/null
+++ b/test/medium/test_641_design_circular_deque.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/641_design_circular_deque'
+require 'minitest/autorun'
+
+class DesignCircularDequeTest < ::Minitest::Test
+  def test_default_one
+    my_circular_deque = ::MyCircularDeque.new(3)
+
+    assert(my_circular_deque.insert_last(1))
+    assert(my_circular_deque.insert_last(2))
+    assert(my_circular_deque.insert_front(3))
+    assert(!my_circular_deque.insert_front(4))
+
+    assert_equal(2, my_circular_deque.get_rear)
+
+    assert(my_circular_deque.is_full)
+    assert(my_circular_deque.delete_last)
+    assert(my_circular_deque.insert_front(4))
+
+    assert_equal(4, my_circular_deque.get_front)
+  end
+
+  def test_additional_one
+    my_circular_deque = ::MyCircularDeque.new(5)
+
+    assert(my_circular_deque.insert_front(7))
+    assert(my_circular_deque.insert_last(0))
+
+    assert_equal(7, my_circular_deque.get_front)
+
+    assert(my_circular_deque.insert_last(3))
+    assert_equal(3, my_circular_deque.get_rear)
+
+    assert(my_circular_deque.insert_front(9))
+
+    assert_equal(3, my_circular_deque.get_rear)
+    assert_equal(9, my_circular_deque.get_front)
+    assert_equal(9, my_circular_deque.get_front)
+
+    assert(my_circular_deque.delete_last)
+
+    assert_equal(0, my_circular_deque.get_rear)
+
+    assert(my_circular_deque.delete_last)
+    assert(my_circular_deque.delete_last)
+
+    assert(my_circular_deque.insert_front(9))
+    assert(my_circular_deque.delete_front)
+    assert(my_circular_deque.delete_last)
+  end
+end