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

原文：http://www.cnblogs.com/mrpod2g/p/4602728.html