# (11) STL: Happy Number

[Question Link](https://leetcode.com/problems/happy-number/)  and  [Solution Link](https://leetcode.com/submissions/detail/617744472/) 

**Difficulty**: Easy

**Problem Statement**: Given a number we need to find the sum of the square of digits of the number till the resultant is 1. If the resultant is 1 return true else false.

**Approach**: We will use a set to maintain unique elements. If at any point we get repeated elements we break out of the loop. Else we simply perform computation and check for the condition.

```
bool isHappy(int n)
{
    set<int> st;
    int s, sum;
    while (st.find(n) == st.end())
    {
        if (n == 1) return true;
        st.insert(n);
        s = n, sum = 0;
        while (s)
        {
            sum += pow(s % 10, 2);
            s /= 10;
        }
        n = sum;
    }
    return false;
}
``` 

**Subscribe to the newsletter so that you never miss any post or update just like this one.**

You can follow me on Hashnode for:

- Daily Data Structure and Algorithm based questions
- Getting knowledge of various development-related tools, concepts, and practices

 [Twitter](https://twitter.com/_Arsalaan_) ,  [GitHub](https://github.com/arsalanhub) ,  [LinkedIn](https://www.linkedin.com/in/mohammadarsalan/)  and  [Hashnode](https://hashnode.com/@mohdarsalan)