(LeetCode 202) Happy Number

Q:
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

题意大概是，给你一个整数，将它替换为他各个位的平方和，如此重复，如果她能够最后变成1.那么他就是Happy Number。否则他就会无限循环下去。

solution:
判断它是Happy Number相信大家都会，可是怎么判定它不是Happy Number呢？
我想了半天，后来发现题目里面已经给了提示，因为他最终会无限循环，就是说最后会有重复的数出现。这里我也学会使用unordered_map了。

class Solution {public:    bool isHappy(int n) {        unordered_map<int,bool>check;        check[n]=true;        while(n!=1){            n = decomposite(n);            if(check[n]==true)return false;            check[n]=true;        }        return true;    }    int decomposite(int n){        int res=0;        while(n){            int m=n%10;            n/=10;            res += m*m;        }        return res;    }};

Reference Link:
http://www.cnblogs.com/ganganloveu/p/4469917.html