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

以十進位為例： 2 8 → 2²+8²=68 → 6²+8²=100 → 1²+0²+0²=1 3 2 → 3²+2²=13 → 1²+3²=10 → 1²+0²=1 3 7 → 3²+7²=58 → 5²+8²=89 → 8²+9²=145 → 1²+4²+5²=42 → 4²+2²=20 → 2²+0²=4 → 4²=16 → 1²+6²=37…… 因此28和32是快樂數，而在37的計算過程中，37重覆出現，繼續計算的結果只會是上述數字的迴圈，不會出現1，因此37不是快樂數。 不是快樂數的數稱為不快樂數（unhappy number），所有不快樂數的數位平方和計算，最後都會進入 4 → 16 → 37 → 58 → 89 → 145 → 42 → 20 → 4 的迴圈中。         所以，Unhappy Number 最好肯定都會進入某種迴圈，如上面的37.  由此，我們的解法如下：

class Solution {
public:
    bool isHappy(int n) {
        if(n<0)
            return false;
        if(n == 1)
            return true;
        
        unordered_set<int> array;
        array.insert(n);
        int s;
        
        while(true)
        {
            s=0;
            while(n)
            {
                s += (n%10)*(n%10);
                n /= 10;
            }
            if(s == 1)
                return true;
            else if(array.find(s) != array.end())
                return false;
            n = s;
            array.insert(n);
        }
        
    }
};