Write an algorithm to determine if a number `n` is a happy number.
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.
- Repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1.
- A number for which this process ends in 1 is a happy number.
Return `true` if `n` is a happy number, and `false` if not.