leetcode 202

202. Happy Number

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

利用递归求解，出口设置为参数为1返回true，参数出现过则返回false.

代码如下：

 class Solution {
 public:
     int sum;
     vector<int> re;
     bool isHappy(int n) {
         if(n == )
         {
             re.clear();
             return true;
         }
         else
         {
             int count = ;
             for(int i = ; i < re.size(); i++)
             {
                 if(n == re[i])
                 {
                     count++;
                 }
                 if(count > )
                 {
                     return false;
                 }
             }
         }
         sum = ;
         while(n)
         {
             sum += (n%) * (n%);
             n /= ;
         }
         re.push_back(sum);
         return isHappy(sum);
     }
 };