Happy Number

各种进制的转换，一直是自己的软肋，需要好好整理总结一下。

sum = sum + (n%10)*(n%10);
            n = n / 10;

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