Happy Number问题及解法

问题描述：

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.

 19 is a happy number

• 1² + 9² = 82
• 8² + 2² = 68
• 6² + 8² = 100
• 1² + 0² + 0² = 1

问题分析：

非happy数会有一个特点，在循环过程中会出现4这个值，依次我们只需要将1和4作为跳出循环的条件即可。

过程详见代码：

class Solution {
public:
    bool isHappy(int n) {
        while(n != 1 && n != 4)
        {
        	int t = 0;
        	while(n)
        	{
				t += (n % 10) * (n % 10);
				n /= 10;
			}
			n = t;
		}
		return n == 1;
    }
};