diff --git a/README.md b/README.md
index 418a0e0d..c9d764ef 100644
--- a/README.md
+++ b/README.md
@@ -720,6 +720,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 1823. Find the Winner of the Circular Game                                          | [Link](https://leetcode.com/problems/find-the-winner-of-the-circular-game/)                                          | [Link](./lib/medium/1823_find_the_winner_of_the_circular_game.rb)                                          | [Link](./test/medium/test_1823_find_the_winner_of_the_circular_game.rb)                                          |
 | 1829. Maximum XOR for Each Query                                                    | [Link](https://leetcode.com/problems/maximum-xor-for-each-query/)                                                    | [Link](./lib/medium/1829_maximum_xor_for_each_query.rb)                                                    | [Link](./test/medium/test_1829_maximum_xor_for_each_query.rb)                                                    |
 | 1834. Single-Threaded CPU                                                           | [Link](https://leetcode.com/problems/single-threaded-cpu/)                                                           | [Link](./lib/medium/1834_single_threaded_cpu.rb)                                                           | [Link](./test/medium/test_1834_single_threaded_cpu.rb)                                                           |
+| 1845. Seat Reservation Manager                                                      | [Link](https://leetcode.com/problems/seat-reservation-manager/)                                                      | [Link](./lib/medium/1845_seat_reservation_manager.rb)                                                      | [Link](./test/medium/test_1845_seat_reservation_manager.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 5aa8730c..f79783ac 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 = '8.8.6'
+  s.version = '8.8.7'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/1845_seat_reservation_manager.rb b/lib/medium/1845_seat_reservation_manager.rb
new file mode 100644
index 00000000..5589edc1
--- /dev/null
+++ b/lib/medium/1845_seat_reservation_manager.rb
@@ -0,0 +1,61 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/seat-reservation-manager/
+class SeatManager
+  # @param {Integer} n
+  def initialize(n)
+    @heap = (1..n).to_a
+  end
+
+  # @return {Integer}
+  def reserve
+    min = @heap[0]
+    last = @heap.pop
+
+    unless @heap.empty?
+      @heap[0] = last
+      heapify_down(0)
+    end
+
+    min
+  end
+
+  # @param {Integer} seat_number
+  # @return {Void}
+  def unreserve(seat_number)
+    @heap << seat_number
+    heapify_up(@heap.size - 1)
+  end
+
+  private
+
+  # @param {Integer} index
+  # @return {Void}
+  def heapify_down(index)
+    smallest = index
+    left = 2 * index + 1
+    right = 2 * index + 2
+
+    smallest = left if left < @heap.size && @heap[left] < @heap[smallest]
+
+    smallest = right if right < @heap.size && @heap[right] < @heap[smallest]
+
+    return unless smallest != index
+
+    @heap[index], @heap[smallest] = @heap[smallest], @heap[index]
+    heapify_down(smallest)
+  end
+
+  # @param {Integer} index
+  # @return {Void}
+  def heapify_up(index)
+    return if index.zero?
+
+    parent = (index - 1) / 2
+
+    return unless @heap[index] < @heap[parent]
+
+    @heap[index], @heap[parent] = @heap[parent], @heap[index]
+    heapify_up(parent)
+  end
+end
diff --git a/test/medium/test_1845_seat_reservation_manager.rb b/test/medium/test_1845_seat_reservation_manager.rb
new file mode 100644
index 00000000..92f83aba
--- /dev/null
+++ b/test/medium/test_1845_seat_reservation_manager.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/1845_seat_reservation_manager'
+require 'minitest/autorun'
+
+class SeatReservationManagerTest < ::Minitest::Test
+  def test_default_one
+    seat_manager = ::SeatManager.new(5)
+
+    assert_equal(1, seat_manager.reserve)
+    assert_equal(2, seat_manager.reserve)
+
+    seat_manager.unreserve(2)
+
+    assert_equal(2, seat_manager.reserve)
+    assert_equal(3, seat_manager.reserve)
+    assert_equal(4, seat_manager.reserve)
+    assert_equal(5, seat_manager.reserve)
+
+    seat_manager.unreserve(5)
+  end
+end