Happy Number

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

方法：哈希记录出现的次数防止出现循环

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