Happy Numbers

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

Solution

   bool isHappy(int n) {

        int sumSquare = 0;

        int temp;

bool flag = true;

bool result = false;

set<int> HappyList;

pair<set<int>::iterator,bool> ret;

while (flag == true)

{

while (n > 0)

{

temp=n%10;

sumSquare = sumSquare + (temp*temp);

n = n/10;

}

ret = HappyList.insert(sumSquare);

if (ret.second == false)

{

flag = false;

}

        

if (sumSquare == 1)

{

result = true;

return result;

}

n = sumSquare;

sumSquare = 0;

}

        

       

        return false;

    }

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