https://leetcode.com/problems/happy-number/


Runtime: 46 ms, faster than 70.82% of Python3 online submissions for Happy Number.

Memory Usage: 13.8 MB, less than 61.15% of Python3 online submissions for Happy Number.


```
class Solution:
    def isHappy(self, n: int) -> bool:
        #3:40
        old_list = []
        while True:
            if len(old_list) > 10:
                return False
            string_n = str(n)
            sum_ = 0
            for single_one in string_n:
                sum_ += int(single_one)**2
            n = sum_
            old_list.append(n)
            if n == 1:
                return True
            if n < 1:
                return False
        #3:43
        #debug until 3:49
```