lintcode easy Happy Number

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

1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

public class Solution {
    /**
     * @param n an integer
     * @return true if this is a happy number or false
     */

    boolean[] visited=new boolean[100];

    public boolean isHappy(int n) {
        if (n<visited.length&&visited[n])
            return false;

        if(n<visited.length)
        {
            visited[n]=true;
        }

       int sum=0;
       while(n > 0)
       {
           int d = n % 10;
           sum += d * d;
           n /= 10;
       }

       if (sum == 1)
        return true;

       return isHappy(sum);
    }
}