diff --git a/README.md b/README.md
index 6b1d3f8f..fbdf1af0 100644
--- a/README.md
+++ b/README.md
@@ -704,6 +704,7 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 1525. Number of Good Ways to Split a String                                         | [Link](https://leetcode.com/problems/number-of-good-ways-to-split-a-string/)                                         | [Link](./lib/medium/1525_number_of_good_ways_to_split_a_string.rb)                                         | [Link](./test/medium/test_1525_number_of_good_ways_to_split_a_string.rb)                                         |
 | 1529. Minimum Suffix Flips                                                          | [Link](https://leetcode.com/problems/minimum-suffix-flips/)                                                          | [Link](./lib/medium/1529_minimum_suffix_flips.rb)                                                          | [Link](./test/medium/test_1529_minimum_suffix_flips.rb)                                                          |
 | 1530. Number of Good Leaf Nodes Pairs                                               | [Link](https://leetcode.com/problems/number-of-good-leaf-nodes-pairs/)                                               | [Link](./lib/medium/1530_number_of_good_leaf_nodes_pairs.rb)                                               | [Link](./test/medium/test_1530_number_of_good_leaf_nodes_pairs.rb)                                               |
+| 1557. Minimum Number of Vertices to Reach All Nodes                                 | [Link](https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/)                                 | [Link](./lib/medium/1557_minimum_number_of_vertices_to_reach_all_nodes.rb)                                 | [Link](./test/medium/test_1557_minimum_number_of_vertices_to_reach_all_nodes.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 a65a84bd..e163d708 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 = '8.7.0'
+  s.version = '8.7.1'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/1557_minimum_number_of_vertices_to_reach_all_nodes.rb b/lib/medium/1557_minimum_number_of_vertices_to_reach_all_nodes.rb
new file mode 100644
index 00000000..bf455f52
--- /dev/null
+++ b/lib/medium/1557_minimum_number_of_vertices_to_reach_all_nodes.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/minimum-number-of-vertices-to-reach-all-nodes/
+# @param {Integer} n
+# @param {Integer[][]} edges
+# @return {Integer[]}
+def find_smallest_set_of_vertices(n, edges)
+  result = []
+  reachable = ::Array.new(n, 0)
+
+  edges.each { |edge| reachable[edge[1]] = 1 }
+
+  (0...n).each { |i| result << i if reachable[i].zero? }
+
+  result
+end
diff --git a/test/medium/test_1557_minimum_number_of_vertices_to_reach_all_nodes.rb b/test/medium/test_1557_minimum_number_of_vertices_to_reach_all_nodes.rb
new file mode 100644
index 00000000..de46006d
--- /dev/null
+++ b/test/medium/test_1557_minimum_number_of_vertices_to_reach_all_nodes.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/1557_minimum_number_of_vertices_to_reach_all_nodes'
+require 'minitest/autorun'
+
+class MinimumNumberOfVerticesToReachAllNodesTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      [0, 3],
+      find_smallest_set_of_vertices(
+        6,
+        [
+          [0, 1],
+          [0, 2],
+          [2, 5],
+          [3, 4],
+          [4, 2]
+        ]
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      [0, 2, 3],
+      find_smallest_set_of_vertices(
+        5,
+        [
+          [0, 1],
+          [2, 1],
+          [3, 1],
+          [1, 4],
+          [2, 4]
+        ]
+      )
+    )
+  end
+end