---
# System prepended metadata

title: 'Happy Number <img src="https://img.shields.io/badge/-easy-brightgreen">'
tags: [data_structure_python]

---

---
tags: data_structure_python
---

# Happy Number <img src="https://img.shields.io/badge/-easy-brightgreen">

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.

<ins>**Example:**</ins>

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

# Solution

### Solution 1: First approach
```python=
class Solution:
    def isHappy(self, n: int) -> bool:
        record = []
        while True:
            res = 0
            while n > 0:
                res += (n % 10)**2
                n = n // 10
                
            if res == 1:
                return True
            if res in record:
                return False
            else:
                record.append(res)
                
            n = res
```

### Solution 2: [Math approach](https://en.wikipedia.org/wiki/Happy_number)

```python=
class Solution:
    def isHappy(self, n: int) -> bool:
        while n != 1:
            n = sum([int(i) ** 2 for i in str(n)])
            if n == 4:
                return False
        
        return True
```