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
1^2 + 9^2 = 82 8^2 + 2^2 = 68 6^2 + 8^2 = 100 1^2 + 0^2 + 0^2 = 1
思路：就是暴力解，根据定义将数字拆成个数部分，不断的除10，获取所有单独的数字，然后对其求平方,将所有数字保存到一个set里面，当set有重复表示这个不是一个happy number.
class Solution { public: bool isHappy(int n) { set<int> iset; while(1) { vector<int> ivec; while(n>=10) { int num = n % 10; ivec.push_back(num); n = n/10; } ivec.push_back(n); int res=0; for(int i = 0; i < ivec.size(); ++i) { res += ivec[i]*ivec[i]; } n=res; if(res == 1) { break; } set<int>::iterator iter; iter = iset.find(res); if(iter == iset.end()) { iset.insert(res); }else{ return false; } } return true; } };