happyNumber.js

////////////////////////////////////////////////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:
// 12 + 92 = 82
// 82 + 22 = 68
// 62 + 82 = 100
// 12 + 02 + 02 = 1
// Example 2:
// Input: n = 2
// Output: false
/**
 * @param {number} n
 * @return {boolean}
 */
 const isHappy = function(n) {
    const obj = {};
    let sum = n;

    while (!obj[sum]) {
        obj[sum] = true;

        const nums = String(sum).split('');
        sum = nums.reduce((acc, val) => acc + Math.pow(Number(val), 2), 0);

        if (sum === 1) {
            return true;
        }
    }

    return false;
};

// console.log(isHappy(19));
// console.log(isHappy(2));