Back to all solutions
#202 - Happy Number
Problem Description
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.
Solution
/**
* @param {number} n
* @return {boolean}
*/
var isHappy = function(n) {
while (n !== 1) {
n = [...String(n)].reduce((sum, digit) => sum + digit ** 2, 0);
if (n === 4) {
return false;
}
}
return true;
};