LeetCode 202 - Happy Number

Write an algorithm to determine if a number 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.

Example: 19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

public boolean isHappy(int n) {
    Set<Integer> set = new HashSet<>();
    while(set.add(n)) {
        n = sumSquares(n);
        if(n == 1) return true;
    }
    return false;
}

private int sumSquares(int n) {
    int sum = 0;
    while(n != 0) {
        int digit = n % 10;
        sum += digit * digit;
        n /= 10;
    }
    return sum;
}