From 6cc535ea847d1ee8b09298d875f0ec4d858b735a Mon Sep 17 00:00:00 2001
From: fartem <jaman.smlnsk@gmail.com>
Date: Wed, 6 Nov 2024 08:58:53 +0300
Subject: [PATCH] 2024-11-06 v. 6.9.7: added "394. Decode String"

---
 README.md                             |  1 +
 leetcode-ruby.gemspec                 |  2 +-
 lib/medium/394_decode_string.rb       | 23 ++++++++++++++++++
 test/medium/test_394_decode_string.rb | 34 +++++++++++++++++++++++++++
 4 files changed, 59 insertions(+), 1 deletion(-)
 create mode 100644 lib/medium/394_decode_string.rb
 create mode 100644 test/medium/test_394_decode_string.rb

diff --git a/README.md b/README.md
index 1fdbd7fa..772eea59 100644
--- a/README.md
+++ b/README.md
@@ -562,3 +562,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 380. Insert Delete GetRandom O(1)                               | [Link](https://leetcode.com/problems/insert-delete-getrandom-o1/)                                 | [Link](./lib/medium/380_insert_delete_getrandom_o1.rb)                                 | [Link](./test/medium/test_380_insert_delete_getrandom_o1.rb)                                 |
 | 382. Linked List Random Node                                    | [Link](https://leetcode.com/problems/linked-list-random-node/)                                    | [Link](./lib/medium/382_linked_list_random_node.rb)                                    | [Link](./test/medium/test_382_linked_list_random_node.rb)                                    |
 | 388. Longest Absolute File Path                                 | [Link](https://leetcode.com/problems/longest-absolute-file-path/)                                 | [Link](./lib/medium/388_longest_absolute_file_path.rb)                                 | [Link](./test/medium/test_388_longest_absolute_file_path.rb)                                 |
+| 394. Decode String                                              | [Link](https://leetcode.com/problems/decode-string/)                                              | [Link](./lib/medium/394_decode_string.rb)                                              | [Link](./test/medium/test_394_decode_string.rb)                                              |
diff --git a/leetcode-ruby.gemspec b/leetcode-ruby.gemspec
index f90d30db..bcf2320e 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 = '6.9.6'
+  s.version = '6.9.7'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'
diff --git a/lib/medium/394_decode_string.rb b/lib/medium/394_decode_string.rb
new file mode 100644
index 00000000..3bbee4fe
--- /dev/null
+++ b/lib/medium/394_decode_string.rb
@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/decode-string/
+# @param {String} s
+# @return {String}
+def decode_string(s)
+  last = s.rindex('[')
+
+  return s if last.nil?
+
+  p = last - 1
+  while p >= 0
+    break unless s[p] =~ /\d/
+
+    p -= 1
+  end
+
+  count = s[p + 1..last - 1].to_i
+  r_s = s[last + 1...s.index(']', last)] * count
+  s = s.sub(s[p + 1..s.index(']', p + 1)], r_s)
+
+  decode_string(s)
+end
diff --git a/test/medium/test_394_decode_string.rb b/test/medium/test_394_decode_string.rb
new file mode 100644
index 00000000..522ca172
--- /dev/null
+++ b/test/medium/test_394_decode_string.rb
@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/394_decode_string'
+require 'minitest/autorun'
+
+class DecodeStringTest < ::Minitest::Test
+  def test_default_one
+    assert_equal(
+      'aaabcbc',
+      decode_string(
+        '3[a]2[bc]'
+      )
+    )
+  end
+
+  def test_default_two
+    assert_equal(
+      'accaccacc',
+      decode_string(
+        '3[a2[c]]'
+      )
+    )
+  end
+
+  def test_default_three
+    assert_equal(
+      'abcabccdcdcdef',
+      decode_string(
+        '2[abc]3[cd]ef'
+      )
+    )
+  end
+end