happyNumber.cpp

// Every number > 9 on sum of squared expansion will reduce to number < 9
// In [0-9],  there are only two cases when number < 9 and it is happy number i.e 1 and 7

class Solution {
public:;
    
    int sumSquare(int n) {
        int sum = 0;
        while(n !=0){
            sum += (n%10) * (n%10);
            n = n/10;
        }
        return sum;
    }
    
    bool isHappy(int n) {
        int sum = sumSquare(n);
        while(true){
            if(sum == 1 || sum == 7) return true;
            if(sum/10 == 0) return false;
            sum = sumSquare(sum);
        }
        
        return false;
    }
};