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
Constraints:
1 <= n <= 231 - 1
Idea:
create a function to calculate the sum of the squares of its digits.
use fast and slow pointers traversal concept (the other one execute function twice) to check if they can reach 1 (means it is happy number)
Solution:
/**
* @param {number} n
* @return {boolean}
*/
var isHappy = function(n) {
let slow = n;
let fast = n;
do {
slow = squareSum(slow);
fast = squareSum(squareSum(fast));
} while (slow !== fast);
return fast === 1;
};
var squareSum = function(n) {
let sum = 0;
while(n) {
sum += (n % 10) * (n % 10);
n = parseInt(n / 10);
}
return sum;
};