LeetCode:Happy Number

题目描述：

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.

Example: 19 is a happy number

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

思路：用一个set记录计算的过程中出现的数，如果在得到1之前有重复的数出现，则表示这个数不是一个happy数，否则就是happy数。

代码:

class Solution{public:bool isHappy(int n){set<int> number_set;number_set.insert(n);while(true){int m = 0;while(n != 0){m = m + (n%10) * (n%10);n = n/10;}if(m == 1)return true;else{if(number_set.find(m) != number_set.end())return false;else{number_set.insert(m);n = m;}}}}};