202. Happy Number

https://leetcode.com/problems/happy-number/

 

class Solution {
public:
    
    int calc(int n) {
        int sol = 0;
        while (n) {
            int cand = n % 10;
            sol = sol + pow(cand, 2);
            n = n / 10;
        }
        return sol;
    }

    bool isHappy(int n) {
        while (n) {
            int cand = calc(n);

            if (1 <= cand && cand <= 9) {
                if (cand == 1 || cand == 7) 
                    return true;
                else 
                    return false;
            }
            n = cand;
        }
        return false;
    }

};