count-and-say.js

undefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefinedundefined/**

• @param {number} n
• @return {string} */

Solution:

// 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"

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

    for (let i = 1; i < n; i++) {
        res = say(res);
    }

    return res;
}

function say(str) {
    let res = '';
    let count = 0;
    let num = str[0];

    for (let i = 0; i < str.length; i++) {
        if (str[i] === num) {
            count++;
        } else {
            res += count + str[i - 1];
            count = 1;
            num = str[i];
        }
    }

    return res + count + num;
}

Reference: ..