2024-12-17 v. 7.3.6: added "647. Palindromic Substrings"

Author: fartem

README.md

@@ -600,3 +600,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 622. Design Circular Queue                                      | [Link](https://leetcode.com/problems/design-circular-queue/)                                      | [Link](./lib/medium/622_design_circular_queue.rb)                                      | [Link](./test/medium/test_622_design_circular_queue.rb)                                      |
 | 623. Add One Row to Tree                                        | [Link](https://leetcode.com/problems/add-one-row-to-tree/)                                        | [Link](./lib/medium/623_add_one_row_to_tree.rb)                                        | [Link](./test/medium/test_623_add_one_row_to_tree.rb)                                        |
 | 641. Design Circular Deque                                      | [Link](https://leetcode.com/problems/design-circular-deque/)                                      | [Link](./lib/medium/641_design_circular_deque.rb)                                      | [Link](./test/medium/test_641_design_circular_deque.rb)                                      |
+| 647. Palindromic Substrings                                     | [Link](https://leetcode.com/problems/palindromic-substrings/)                                     | [Link](./lib/medium/647_palindromic_substrings.rb)                                     | [Link](./test/medium/test_647_palindromic_substrings.rb)                                     |

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 = '7.3.5'
+  s.version = '7.3.6'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/647_palindromic_substrings.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/palindromic-substrings/
+# @param {String} s
+# @return {Integer}
+def count_substrings(s)
+  count = 0
+  s.size.times do |i|
+    count += palindrome_count_for_string(s, i, i)
+    count += palindrome_count_for_string(s, i, i + 1)
+  end
+
+  count
+end
+
+private
+
+# @param {String} s
+# @param {Integer} left
+# @param {Integer} right
+# @return {Integer}
+def palindrome_count_for_string(s, left, right)
+  count = 0
+  while left >= 0 && right < s.length && s[left] == s[right]
+    count += 1
+    left -= 1
+    right += 1
+  end
+
+  count
+end

test/medium/test_647_palindromic_substrings.rb

@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/647_palindromic_substrings'
+require 'minitest/autorun'
+
+class PalindromicSubstringsTest < ::Minitest::Test
+  def test_default_one = assert_equal(3, count_substrings('abc'))
+
+  def test_default_two = assert_equal(6, count_substrings('aaa'))
+end