2490-circular-sentence.js

/**
 * 2490. Circular Sentence
 * https://leetcode.com/problems/circular-sentence/
 * Difficulty: Easy
 *
 * 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.
 */

/**
 * @param {string} sentence
 * @return {boolean}
 */
var isCircularSentence = function(sentence) {
  const match = sentence.match(/^\w$|^(\w).*\1$/) !== null;
  const count = sentence.match(/(\w)(?=\s\1)/g)?.length || 0;

  return match && count === sentence.split(/\s/).length - 1;
};