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

总体来说，还是比较好理解的，主要是怎么判断进入了一个死循环，以及求每个数字的平方和

<span style="font-size:18px;">public class Solution {
    public boolean isHappy(int n) {
        if(n == 0){
            return false;
        }
        Set<Integer> set = new HashSet<Integer>();//存储平方和，判断是否进入了一个死循环
        Queue<Integer> queue = new LinkedList<Integer>();//存储n分解出来的数字
        while(n != 1){
            if(set.contains(n)){
                return false;//进入了一个circle
            }else{
                set.add(n);
            }
            while(n != 0){
                queue.offer(n % 10);
                n = n / 10;
            }
            n = 0;
            while(queue.peek() != null){
                int tmp = queue.poll();
                n = n + tmp*tmp;
            }
        }
        return true;
    }
}</span>

Happy Number

原文：http://blog.csdn.net/havedream_one/article/details/45241685