Happy_Number.js

/**
Happy Number
https://leetcode.com/problems/happy-number/

Write an algorithm to determine if a number n is happy.

A happy number is a number defined by the following process:

    Starting with any positive integer, replace the number by the sum of the squares of its digits.
    Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1.
    Those numbers for which this process ends in 1 are happy.

Return true if n is a happy number, and false if not.

Example 1:
Input: n = 19
Output: true
Explanation:
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

Example 2:
Input: n = 2
Output: false

Example 3:
Input n = 7
Output = true
Explanation:
7^2 = 49
4^2 + 9^2 = 97
9^2 + 7^2 = 130
1^2 + 3^2 + 0^2 = 10
1^2 + 0^2 = 1

 */

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function(n) {
  return checkHappyNumber(n);
};

function checkHappyNumber(n){
  let strNumber = n.toString();
  let splitNumber = strNumber.split("");
  if(splitNumber.length <= 1){
    return (n === 1 || n === 7)? true:false;
  }
  const digit = splitNumber.reduce((a,b)=> parseInt(a) + Math.pow(parseInt(b),2),0);
  return checkHappyNumber(digit);
}

module.exports.isHappy = isHappy;