## Description

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:**

```
Input: 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
```

## Solutions

### 1. Hash Table

```
# Time: O(n)
# Space: O(n)
class Solution:
def isHappy(self, n: int) -> bool:
visited = set()
visited.add(n)
while n != 1:
strs = str(n)
ssum = 0
for num in strs:
ssum += int(num) ** 2
if ssum in visited:
return False
else:
visited.add(ssum)
n = ssum
return True
# 401/401 cases passed (36 ms)
# Your runtime beats 34.19 % of python3 submissions
# Your memory usage beats 100 % of python3 submissions (12.7 MB)
```