countAndSay.js

/*
 * 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}
 */
var countAndSay = function(n) {
    if (n === 1){
        return "1";
    }
    
    let prevStr = countAndSay(n-1);
    let mapArr = [];
    let counter = 0;
    for(char of prevStr){
        if (counter === 0){
            mapArr.push({val: char, count: 1});
        } else {
            let prevMap = mapArr[mapArr.length-1];
            if (prevMap.val === char){
                mapArr[mapArr.length-1].count++;
            } else {
                mapArr.push({val: char, count: 1});
            }   
        }
        
        counter++;
    }
    
    let str = "";
    for(map of mapArr){
        str += map.count;
        str += map.val;
    }

    return str;
};