2490. Circular Sentence (#193)

* 2490. Circular Sentence

* Fix: remove 1957

Author: remy727

README.md

@@ -495,6 +495,7 @@
 | 2466 | Count Ways To Build Good Strings | [Ruby](./algorithms/ruby/2466-count-ways-to-build-good-strings.rb) | Medium |
 | 2477 | Minimum Fuel Cost to Report to the Capital | [Ruby](./algorithms/ruby/2477-minimum-fuel-cost-to-report-to-the-capital.rb) | Medium |
 | 2483 | Minimum Penalty for a Shop | [Ruby](./algorithms/ruby/2483-minimum-penalty-for-a-shop.rb) | Medium |
+| 2490 | Circular Sentence | [Ruby](./algorithms/ruby/2490-circular-sentence.rb) | Easy |
 | 2492 | Minimum Score of a Path Between Two Cities | [Ruby](./algorithms/ruby/2492-minimum-score-of-a-path-between-two-cities.rb) | Medium |
 | 2501 | Longest Square Streak in an Array | [Ruby](./algorithms/ruby/2501-longest-square-streak-in-an-array.rb) | Medium |
 | 2542 | Maximum Subsequence Score | [Ruby](./algorithms/ruby/2542-maximum-subsequence-score.rb) | Medium |

algorithms/ruby/2490-circular-sentence.rb

@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+# 2490. Circular Sentence
+# Easy
+# https://leetcode.com/problems/circular-sentence
+
+=begin
+A sentence is a list of words that are separated by a single space with no leading or trailing spaces.
+* For example, "Hello World", "HELLO", "hello world hello world" are all sentences.
+Words consist of only uppercase and lowercase English letters. Uppercase and lowercase English letters are considered different.
+A sentence is circular if:
+* The last character of a word is equal to the first character of the next word.
+* The last character of the last word is equal to the first character of the first word.
+For example, "leetcode exercises sound delightful", "eetcode", "leetcode eats soul" are all circular sentences. However, "Leetcode is cool", "happy Leetcode", "Leetcode" and "I like Leetcode" are not circular sentences.
+Given a string sentence, return true if it is circular. Otherwise, return false.
+
+Example 1:
+Input: sentence = "leetcode exercises sound delightful"
+Output: true
+Explanation: The words in sentence are ["leetcode", "exercises", "sound", "delightful"].
+- leetcode's last character is equal to exercises's first character.
+- exercises's last character is equal to sound's first character.
+- sound's last character is equal to delightful's first character.
+- delightful's last character is equal to leetcode's first character.
+The sentence is circular.
+Example 2:
+Input: sentence = "eetcode"
+Output: true
+Explanation: The words in sentence are ["eetcode"].
+- eetcode's last character is equal to eetcode's first character.
+The sentence is circular.
+Example 3:
+Input: sentence = "Leetcode is cool"
+Output: false
+Explanation: The words in sentence are ["Leetcode", "is", "cool"].
+- Leetcode's last character is not equal to is's first character.
+The sentence is not circular.
+
+Constraints:
+* 1 <= sentence.length <= 500
+* sentence consist of only lowercase and uppercase English letters and spaces.
+* The words in sentence are separated by a single space.
+* There are no leading or trailing spaces.
+=end
+
+# @param {String} sentence
+# @return {Boolean}
+def is_circular_sentence(sentence)
+  n = sentence.length
+
+  return false if sentence[0] != sentence[n - 1]
+
+  (1..n - 2).each do |i|
+    if sentence[i] == " "
+      return false if sentence[i - 1] != sentence[i + 1]
+    end
+  end
+
+  true
+end
+
+# **************** #
+#       TEST       #
+# **************** #
+
+require "test/unit"
+class Test_is_circular_sentence < Test::Unit::TestCase
+  def test_
+    assert_equal true, is_circular_sentence("leetcode exercises sound delightful")
+    assert_equal true, is_circular_sentence("eetcode")
+    assert_equal false, is_circular_sentence("Leetcode is cool")
+  end
+end