count-and-say.js

/**
 * Count and Say
 *
 * The count-and-say sequence is the sequence of integers with the first five terms as following:
 *
 * 1.     1
 * 2.     11
 * 3.     21
 * 4.     1211
 * 5.     111221
 * 1 is read off as "one 1" or 11.
 * 11 is read off as "two 1s" or 21.
 * 21 is read off as "one 2, then one 1" or 1211.
 *
 * Given an integer n, generate the nth term of the count-and-say sequence.
 *
 * Note: Each term of the sequence of integers will be represented as a string.
 *
 * Example 1:
 *
 * Input: 1
 * Output: "1"
 *
 *
 * Example 2:
 *
 * Input: 4
 * Output: "1211"
 * Input Constraints:
 *
 * 1 <= n <= 30
 */

/**
 * @param {number} n
 * @return {string}
 */
var countAndSay = function(n) {
  let s = '1';

  while (n > 1) {
    let count = 0;
    let next = '';

    for (let i = 0; i <= s.length; i++) {
      if (i === s.length || (i > 0 && s[i] !== s[i - 1])) {
        next += count + s[i - 1]; // Say
        count = 0;
      }

      count++; // Count
    }

    s = next;
    n--;
  }

  return s;
};

export { countAndSay };