Journal Archive

2022

/**
 * @param {number} n
 * @return {boolean}
 */
var isHappy = function(n) {
    // helper function to square digits
    const digitSquare = (n) => {
        let ans = 0;
        while (n > 0) {
            let digit = n % 10;
            ans += digit * digit;
            n = Math.floor(n / 10);
        }
        return ans;
    }

    let seen = new Set();
    let number = n;
    while (!seen.has(number)) {
        seen.add(number);
        number = digitSquare(number);
        if (number === 1) return true;
    }
    return false;
};

Day 61: Solving one of LeetCode problems

202. Happy Number Difficulty - Easy

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