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
比较直观的方法，就是一步一步的算咯，这里要注意无限循环无结果的问题：
var isHappy = function(n) {
//比较直观的算法
if (n===1) {
return true;
} else if (n<5) {
return false;
} else {
var sum = 0;
while (n!==0) {
var temp = n%10;
sum += temp*temp;
n = parseInt(n/10);
}
return isHappy(sum);
}
};
还有一种神奇的办法：
使用两个指针，一个快指针一个慢指针，这两个指针相遇的时候如果不是1，那就是有循环咯，就不是欢乐数~
