[easy]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

class Solution {
public:

    bool isHappy(int n) {
    int a[100],len=0;
    while(n>1)
    {
       int sum = 0;
       while(n>0)
       {
           int num = n%10;
           sum += num*num;
           n = n/10;
       }
       if(isFind(sum,a,len) == true) return false;
       a[len++] = sum; //add the num
       n = sum;
    }
    if(n==1) return true;
    else return false;
    }
bool isFind(int sum,int a[],int len)
{
   int i;
   for(i=0;i<len;i++)
   {
       if(a[i]==sum) return true;
   }
   return false;
}
};

不开辟空间的方法（别人的思路）

class Solution {
public:

    bool isHappy(int n) {
    while(n>1)
    {
       int sum = 0;
       while(n>0)
       {
           sum += pow(n%10,2);
           n /=10;
       }
       if(sum==4) return false;
       n = sum;
    }
    return n==1;
    }

};