[leetcode] 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

const int SIZE = 1000;

class Solution
{
private:
  bool isExist(int n)
  {
    for(int i=0; i<SIZE; i++)
      if(A[i] == n)
        return true;

    return false;
  }

public:
  bool isHappy(int n)
  {
    int m = 0, index = 0;
    while(1 != n)
    {
      m = 0;
      while(n)
      {
        m += pow(n%10, 2);
        n /= 10;
      }
      n = m;

      if(isExist(n))
        return false;

      A[index++] = n;
    }

    return true;
  }

private:
  int A[SIZE];
};