202. Happy Number — LeetCode Solution

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, and 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 numbers.

Return True if n is a happy number, and False if not.

Example:

Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

Here is my solution:

class Solution {
    public boolean isHappy(int n) {
        Set<Integer> visited = new HashSet<>();
        
        while (n != 1) {
            int current = n, sum = 0;
            while (current != 0) {
                int last = current % 10;
                sum += last * last;
                current = current /10;
            }
            if (visited.contains(sum)) {
                return false;
            }
            visited.add(sum);
            n = sum;
        }
        
        return true;
    }
}

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