From a8384a1d5cc2719d4b94ac246e468cf8ca9f57f4 Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Thu, 18 Apr 2024 07:29:20 +0300
Subject: [PATCH] 2024-04-18 v. 5.4.9: added "2309. Greatest English Letter in
 Upper and Lower Case"

---
 README.md                                     |  1 +
 leetcode-ruby.gemspec                         |  2 +-
 ..._english_letter_in_upper_and_lower_case.rb | 23 +++++++++++++++++++
 ..._english_letter_in_upper_and_lower_case.rb | 13 +++++++++++
 4 files changed, 38 insertions(+), 1 deletion(-)
 create mode 100644 lib/easy/2309_greatest_english_letter_in_upper_and_lower_case.rb
 create mode 100644 test/easy/test_2309_greatest_english_letter_in_upper_and_lower_case.rb

diff --git a/README.md b/README.md
index a89d4c65..ca87f1f8 100644
--- a/README.md
+++ b/README.md
@@ -409,3 +409,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 2293. Min Max Game                                                 | [Link](https://leetcode.com/problems/min-max-game/)                                                 | [Link](./lib/easy/2293_min_max_game.rb)                                                 |
 | 2299. Strong Password Checker II                                   | [Link](https://leetcode.com/problems/strong-password-checker-ii/)                                   | [Link](./lib/easy/2299_strong_password_checker_ii.rb)                                   |
 | 2303. Calculate Amount Paid in Taxes                               | [Link](https://leetcode.com/problems/calculate-amount-paid-in-taxes/)                               | [Link](./lib/easy/2303_calculate_amount_paid_in_taxes.rb)                               |
+| 2309. Greatest English Letter in Upper and Lower Case              | [Link](https://leetcode.com/problems/greatest-english-letter-in-upper-and-lower-case/)              | [Link](./lib/easy/2309_greatest_english_letter_in_upper_and_lower_case.rb)              |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index 0a6058d9..c85d481e 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 = '5.4.8'
+  s.version = '5.4.9'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[bin/leetcode-ruby README.md LICENSE]
   s.executable = 'leetcode-ruby'
diff --git a/lib/easy/2309_greatest_english_letter_in_upper_and_lower_case.rb b/lib/easy/2309_greatest_english_letter_in_upper_and_lower_case.rb
new file mode 100644
index 00000000..e3b345ca
--- /dev/null
+++ b/lib/easy/2309_greatest_english_letter_in_upper_and_lower_case.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/greatest-english-letter-in-upper-and-lower-case/
+# @param {String} s
+# @return {String}
+def greatest_letter(s)
+  upper = {}
+  lower = {}
+
+  s.each_char do |c|
+    if c.match?(/[[:upper:]]/)
+      upper[c] = upper.fetch(c, 0) + 1
+    else
+      lower[c] = lower.fetch(c, 0) + 1
+    end
+  end
+
+  'ZYXWVUTSRQPONMLKJIHGFEDCBA'.each_char do |c|
+    return c if upper.fetch(c, 0).positive? && lower.fetch(c.downcase, 0).positive?
+  end
+
+  ''
+end
diff --git a/test/easy/test_2309_greatest_english_letter_in_upper_and_lower_case.rb b/test/easy/test_2309_greatest_english_letter_in_upper_and_lower_case.rb
new file mode 100644
index 00000000..31fc7a91
--- /dev/null
+++ b/test/easy/test_2309_greatest_english_letter_in_upper_and_lower_case.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/easy/2309_greatest_english_letter_in_upper_and_lower_case'
+require 'minitest/autorun'
+
+class GreatestEnglishLetterInUpperAndLowerCaseTest < ::Minitest::Test
+  def test_default
+    assert_equal('E', greatest_letter('lEeTcOdE'))
+    assert_equal('R', greatest_letter('arRAzFif'))
+    assert_equal('', greatest_letter('AbCdEfGhIjK'))
+  end
+end