#202. 快乐数

int sum(int n)
{
    int sum = 0;
    while(n)
    {
        int curr = n % 10;
        sum += (curr * curr);
        n = n / 10;
    }
    return sum;
}
bool isHappy(int n){
    while(n)
    {
        int curr = sum(n);
        if(curr == 1) return true;
        else if(curr == 4) return false;
        else n = curr;
    }
    return false;
}