# LeetCode 202. Happy Number

## Description

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

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```

## Explanation

Use a hashmap to check if the number gets a cycle.

## Python Solution

``````class Solution:
def isHappy(self, n: int) -> bool:
visited = {}

return self.is_happy_helper(n, visited)

def is_happy_helper(self, n, visited):

if n == 1:
return True

digits_sum = 0
while n != 0:
digit = n % 10
digits_sum += digit**2
n = n // 10

if digits_sum not in visited:
visited[digits_sum] = 1
else:
return False

return self.is_happy_helper(digits_sum, visited)``````
• Time complexity: O(n).
• Space complexity: O(n).