题解 | 快乐数

class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param n int整型 
     * @return bool布尔型
     */
    bool happynum(int n) {
        if (n == 1)     return true;
        if (n == 1000000000) return true;
        set<int>sq = {0,1,4,9,16,25,36,49,64,81};
        vector<int>can_happy = {1,100,68,86,82,28,19,91,10,109,103,130,13,31};

        // 先计算4次，将数字映射到1~162
        int t = n,sum= 0;
        for (int i = 0;i < 4;i++)
        {
            while (t)
            {
                sum+=(t%10)*(t%10);
                t/=10; 
            }
            t = sum;
            sum =0;
        }

        // 
        if (find(can_happy.begin(),can_happy.end(),t) != can_happy.end())
        return true;
        else return false;
    }
};