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
     */
     int Sum(int n)
      {
         int sum = 0;
         while(n)
         {
            int tmp = n % 10;
            sum+=(tmp*tmp);
            n/=10;
         }
         return sum;
      }
    bool happynum(int n) 
    {
        // write code here
         if(n==0)  return false;
        int quick =Sum(n) ,slow = n;//模拟快慢指针
        while(quick != slow )
        {
            quick = Sum(Sum(quick));
            slow = Sum(slow);
        }
        return slow==1;
    }
};