diff --git a/README.md b/README.md
index af8c5359..bc024470 100644
--- a/README.md
+++ b/README.md
@@ -607,3 +607,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 659. Split Array into Consecutive Subsequences                  | [Link](https://leetcode.com/problems/split-array-into-consecutive-subsequences/)                  | [Link](./lib/medium/659_split_array_into_consecutive_subsequences.rb)                  | [Link](./test/medium/test_659_split_array_into_consecutive_subsequences.rb)                  |
 | 662. Maximum Width of Binary Tree                               | [Link](https://leetcode.com/problems/maximum-width-of-binary-tree/)                               | [Link](./lib/medium/662_maximum_width_of_binary_tree.rb)                               | [Link](./test/medium/test_662_maximum_width_of_binary_tree.rb)                               |
 | 669. Trim a Binary Search Tree                                  | [Link](https://leetcode.com/problems/trim-a-binary-search-tree/)                                  | [Link](./lib/medium/669_trim_a_binary_search_tree.rb)                                  | [Link](./test/medium/test_669_trim_a_binary_search_tree.rb)                                  |
+| 677. Map Sum Pairs                                              | [Link](https://leetcode.com/problems/map-sum-pairs/)                                              | [Link](./lib/medium/677_map_sum_pairs.rb)                                              | [Link](./test/medium/test_677_map_sum_pairs.rb)                                              |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index cc3cf3a1..0de0af34 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 = '7.4.2'
+  s.version = '7.4.3'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/677_map_sum_pairs.rb b/lib/medium/677_map_sum_pairs.rb
new file mode 100644
index 00000000..27610435
--- /dev/null
+++ b/lib/medium/677_map_sum_pairs.rb
@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/map-sum-pairs/
+class MapSum
+  # Init
+  def initialize
+    @root = ::MapSum::Node.new
+    @values = {}
+  end
+
+  # @param {String} key
+  # @param {Integer} val
+  # @return {Void}
+  def insert(key, val)
+    delta = val - @values.fetch(key, 0)
+    @values[key] = val
+    curr = @root
+    curr.score += delta
+
+    (0...key.size).each do |i|
+      c = key[i]
+      curr.children[c] = ::MapSum::Node.new unless curr.children.key?(c)
+      curr = curr.children[c]
+      curr.score += delta
+    end
+  end
+
+  # @param {String} prefix
+  # @return {Integer}
+  def sum(prefix)
+    curr = @root
+
+    (0...prefix.size).each do |i|
+      c = prefix[i]
+      curr = curr.children[c]
+
+      return 0 unless curr
+    end
+
+    curr.score
+  end
+
+  # Node realization
+  class Node
+    attr_accessor :children, :score
+
+    # Init
+    def initialize
+      @children = {}
+      @score = 0
+    end
+  end
+end
diff --git a/test/medium/test_677_map_sum_pairs.rb b/test/medium/test_677_map_sum_pairs.rb
new file mode 100644
index 00000000..b27bd8e4
--- /dev/null
+++ b/test/medium/test_677_map_sum_pairs.rb
@@ -0,0 +1,18 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/677_map_sum_pairs'
+require 'minitest/autorun'
+
+class MapSumPairsTest < ::Minitest::Test
+  def test_default_one
+    map_sum = ::MapSum.new
+    map_sum.insert('apple', 3)
+
+    assert_equal(3, map_sum.sum('ap'))
+
+    map_sum.insert('app', 2)
+
+    assert_equal(5, map_sum.sum('ap'))
+  end
+end