Problem

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

Input: 19
Output: true
Explanation: 
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

Code

static int var = [](){
    std::ios::sync_with_stdio(false);
    cin.tie(NULL);
    return 0;
}();
class Solution {
public:
    bool isHappy(int n) {
        vector<int> temp;
        while(1){
            temp.push_back(n);
            int res = 0;
            do{
                int remainder = n%10;
                res += remainder * remainder;
            }while((n/=10)!=0);
            if(res==1)
                return true;
            else if(find(temp.begin(),temp.end(),res)!=temp.end())
                return false;
            else
                n = res;
        }
    }
};

Result

202. Happy Number.png